Edgar Filing: AETHER SYSTEMS INC

FILED PURSUANT TO RULE 424(b)(3)
REGISTRATION NO. 333-56154

PROSPECTUS
----------

2,881,980 SHARES

[AETHER LOGO]

COMMON STOCK

----------------------

The stockholders of Aether Systems, Inc. named in this prospectus are
offering and selling up to 2,881,980 shares of Aether's common stock. The
selling stockholders obtained their shares in connection with our acquisitions
of Cerulean Technology, Inc., Riverbed Technologies, Inc. or RTS Wireless, Inc.
We will receive none of the proceeds from the sale of shares of common stock by
the selling stockholders. We have agreed to bear the expenses of registration of
the shares in this prospectus.

The selling stockholders may offer their shares through public or
private transactions, on or off the Nasdaq National Market at prevailing market
prices or at privately negotiated prices. They may make sales directly to
purchasers or to or through brokers, agents, dealers or underwriters. The
selling stockholders will bear all commissions, and other compensation paid to
brokers in connection with the sale of their shares.

Our shares are traded on the Nasdaq National Market under the symbol
"AETH." On July 30, 2001, the closing sale price of shares of our common stock
was $11.11 per share.

INVESTING IN THE COMMON STOCK INVOLVES RISKS THAT ARE DESCRIBED IN THE
"RISK FACTORS" SECTION BEGINNING ON PAGE 4 OF THIS PROSPECTUS.

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Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.

----------------------

The date of this prospectus is July 31, 2001.
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TABLE OF CONTENTS

PAGE
----

About Aether Systems........................................ 3
Risk Factors................................................ 4
Forward-Looking Statements.................................. 5
Use of Proceeds............................................. 5
Selling Stockholders........................................ 6
Plan of Distribution........................................ 10
Legal Matters............................................... 11
Experts..................................................... 11
Where You Can Find More Information......................... 11

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ABOUT AETHER SYSTEMS

Aether provides technologies that enable businesses to extend their data
and commercial transactions to wireless and mobile handheld devices. At the core
of Aether is a comprehensive family of software products, which we refer to as
our wireless technology foundation, upon which all types of wireless systems for
businesses can be built. Our wireless technology foundation includes wireless
integration, mobile data management and wireless infrastructure software
products. We add to this foundation individual technology components which
include our wireless data engineering and development services, wireless data
hosting, product fulfillment and customer support. These components can be used
separately or in various combinations to extend existing and future business
applications to any handheld device over any wireless network.

The wireless technology foundation gives businesses, systems integrators
and developers the ability to quickly create, deploy and manage wireless
solutions across multiple carrier networks and types of devices. Customers may
choose specific wireless products or services, or have Aether build and manage a
comprehensive wireless solution. In every case, Aether's flexibility to adapt to
a wide variety of systems protects businesses from "betting" on technologies in
a rapidly changing wireless environment.

Our strategy. Our strategy is to be the dominant provider in the United
States and internationally of wireless data services and systems to corporations
by using our engineering expertise, our software products, our hosted solutions
and our other resources. We believe our capabilities and experience have
established us as an early market leader in wireless data services, and a key
element of our strategy is to move quickly into new opportunities to extend our
leadership position. Our strategy also includes the following other key
elements:

- maximize licensing revenue from our mobile data and wireless software;

- win and retain contracts to develop and operate wireless data systems for
large businesses;

- extend the industries and markets to which we provide wireless data
systems and service;

- extend our services to new markets through engineering and strategic
consulting services to businesses that are exploring the implementation
of a wireless data system;

- maintain and strengthen relationships with suppliers and customers; and

- participate in non-core markets through investments and partnerships.

Other information. We are a Delaware corporation. Our principal executive
offices are located at 11460 Cronridge Drive, Owings Mills, Maryland 21117, and
our telephone number is (410) 654-6400. We maintain a Web site at
www.aethersystems.com. Information contained in our Web site does not constitute
a part of this prospectus. All references to "we," "us," "our" or "Aether" in
this prospectus mean Aether Systems, Inc. and its subsidiaries or predecessors.

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RISK FACTORS

Investing in our common stock involves risks. You should carefully
consider the following risks together with the other information contained in
this prospectus and all the information incorporated by reference before
deciding to buy our common stock. A list of factors affecting our operating
results is incorporated herein by reference to our Annual Report on Form 10-K
for the year ended December 31, 2000. The risks below relate solely to this
offering.

OUR STOCK PRICE, LIKE THAT OF MANY TECHNOLOGY COMPANIES, HAS BEEN, AND MAY
CONTINUE TO BE, VOLATILE.

The market price of our common stock has been highly volatile and is likely
to continue to be highly volatile. The trading price of our common stock has
fluctuated from a high of $180.25 to a low of $7.39 in the one year prior to the
date of this prospectus. We are involved in a highly visible, rapidly changing
industry and stock prices in our and similar industries have risen and fallen in
response to a variety of factors, including:

- announcements of new wireless data communications technologies and new
providers of wireless data communications;

- acquisitions of or strategic alliances among providers of wireless data
communications;

- changes in recommendations by securities analysts regarding the results
or prospects of providers of wireless data communications; and

- changes in investor perceptions of the acceptance or profitability of
wireless data communications.

SHARES ELIGIBLE FOR FUTURE SALE BY OUR CURRENT STOCKHOLDERS MAY DEPRESS OUR
SHARE PRICE.

As of July 15, 2001, we had outstanding 40,670,858 shares of common stock.
Sales of a substantial number of our shares of common stock in the public
market -- or the expectation of such sales -- could cause the market price of
our common stock to drop. All the shares sold pursuant to this prospectus will
be, and the shares sold in our initial public offering, our offering in March
2000, our September 2000 offering and the October 2000 shelf registration, are
freely tradable. In addition to the shares covered by this prospectus and
170,852 shares covered by another prospectus, we have agreed to register the
resale of 12,256,189 shares upon demand. An additional 12,458,375 shares
(including some of the shares subject to registration rights) are currently
eligible for sale, subject to a limitation on the number of shares that can be
sold in any three-month period.

We filed a registration statement to register all shares of common stock
that were issued to our employees under our equity incentive plan and intend to
file future registration statements. Shares issued upon exercise of stock
options will be eligible for resale in the public market without restriction. As
of July 15, 2001, options and warrants to purchase 4,310,276 shares of our
common stock and 716,720 shares of restricted stock were issued and outstanding
and covered by the registration statement. In addition, warrants to purchase
893,665 additional shares were issued and outstanding on that date.

THE STOCKHOLDER AGREEMENT AMONG OUR MAJOR STOCKHOLDERS HAS THE EFFECT OF
ALLOWING THEM TO NOMINATE SIX OF OUR SEVEN DIRECTORS, WHICH LIMITS THE ABILITY
OF NEW INVESTORS TO INFLUENCE CONTROL OF AETHER.

NexGen Technologies, L.L.C., Telcom-ATI Investors, L.L.C. and Reuters
MarketClip Holdings Sarl, a subsidiary of Reuters Group Plc. -- who together
hold 24.3% of the shares of our common stock -- entered into a stockholder
agreement that governs voting for our directors. The agreement provides that
each party will vote all of its shares for one director nominated by NexGen, two
directors nominated by Telcom-ATI Investors, two directors nominated jointly by
NexGen and Telcom-ATI Investors and one director nominated by Reuters. As a
result, six directors of our board may be nominated by these major stockholders,
though Telcom-ATI Investors waived its rights in the most recent election of
directors. As we currently have authorized only seven directors, the voting
rights of our stockholders other than these major stockholders may effectively
be meaningfully exercised only in connection with the election of one of

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our directors. In addition to its effect on the voting rights of our new
investors, the stockholder agreement could have the effect of delaying or
preventing a change in control.

WE HAVE ANTI-TAKEOVER DEFENSES THAT COULD DELAY OR PREVENT AN ACQUISITION OF
AETHER AND COULD ADVERSELY AFFECT THE PRICE OF OUR COMMON STOCK.

Provisions of our certificate of incorporation and bylaws and provisions of
Delaware law could delay, defer or prevent an acquisition or change of control
of Aether or otherwise adversely affect the price of our common stock. For
example, our bylaws limit the ability of stockholders to call a special meeting.
Moreover, our certificate of incorporation permits our board to issue shares of
preferred stock without stockholder approval, which means that the board could
issue shares with special voting rights or other provisions that could deter a
takeover. In addition to delaying or preventing an acquisition, the issuance of
a substantial number of preferred shares could adversely affect the price of our
common stock.

FORWARD-LOOKING STATEMENTS

This prospectus includes forward-looking statements within the meaning of
Section 27A of the Securities Act and Section 21E of the Securities Exchange
Act. We have based these forward-looking statements on our current expectations
and projections about future events. In some cases, you can identify
forward-looking statements by terminology such as "may," "will," "should,"
"could," "pending," "potential," "continue," "expects," "anticipates,"
"intends," "plans," "believes," "predicts," "estimates" and similar expressions,
although not all forward-looking statements are identified by these words. These
forward-looking statements are subject to a number of risks, uncertainties and
assumptions about Aether and our industry, including those we describe and
incorporate by reference in the "Risk Factors" section of this prospectus. In
light of these risks, uncertainties and assumptions, the forward-looking events
discussed in this prospectus might not occur. We undertake no obligation to
publicly update or revise any forward-looking statements, whether as a result of
new information, future events or otherwise.

USE OF PROCEEDS

This prospectus relates to shares of our common stock being offered and
sold for the accounts of the selling stockholders named in this prospectus. We
will not receive any proceeds from the shares sold pursuant to this prospectus.

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SELLING STOCKHOLDERS

The following table sets forth certain information with respect to
beneficial ownership of our common stock as of July 15, 2001, as adjusted to
reflect the sale of 2,881,980 shares of common stock pursuant to this
prospectus, as to each stockholder selling shares of our common stock pursuant
to this prospectus.

Except as indicated in the footnotes to this table and under applicable
community property laws, to our knowledge, the persons named in the table have
sole voting and investment power with respect to all shares of common stock. For
the purposes of calculating percent ownership as of July 15, 2001, 40,670,858
shares were issued and outstanding.

The persons selling shares pursuant to this prospectus may include
pledgees, donees, transferees or other successors in interest of the persons
identified below as selling stockholders.

OWNERSHIP OF SHARES OF OWNERSHIP OF
SHARES BEFORE THE COMMON SHARES AFTER THE
OFFERING(1) STOCK OFFERING(1)(3)
----------------- COVERED BY THIS -----------------
SELLING STOCKHOLDERS NUMBER PERCENT PROSPECTUS(2) NUMBER PERCENT
-------------------- ------- ------- --------------- ------- -------

Columbia Riverbed Partners, LLC................ 559,279 1.4% 559,279 0 *
Columbia Capital Equity Partners II (QP),
L.P. ........................................ 514,309 1.3% 514,309 0 *
George Abraham................................. 331 * 331 0 *
Albert Abramson................................ 5,296 * 5,296 0 *
Linda Beers.................................... 2,648 * 2,648 0 *
Berman Enterprises, L.P........................ 9,003 * 9,003 0 *
Gary Berman.................................... 5,296 * 5,296 0 *
Dennis Berman.................................. 5,296 * 5,296 0 *
Delores K. Berman Revocable Trust.............. 3,177 * 3,177 0 *
Helene E. Berman Revocable Trust............... 3,177 * 3,177 0 *
Eric Billings.................................. 2,648 * 2,648 0 *
James H.R. Brady............................... 662 * 662 0 *
Graeme Bush.................................... 3,177 * 3,177 0 *
Lawrence Cirka................................. 5,296 * 5,296 0 *
Neil Cohen..................................... 5,296 * 5,296 0 *
Colony Partners................................ 5,296 * 5,296 0 *
CNF Investment, LLC(4)......................... 42,365 * 42,365 0 *
Clark Enterprises, Inc....................... 29,655 * 29,655 0 *
Robert Flanagan.............................. 4,236 * 4,236 0 *
Lawrence Nossdorf............................ 4,237 * 4,237 0 *
A. James Clark............................... 4,237 * 4,237 0 *
Cyclops Family Partnership..................... 2,648 * 2,648 0 *
Andrew Dixon................................... 1,059 * 1,059 0 *
Andrew & Jean Dixon............................ 1,059 * 1,059 0 *
Robert Duvall.................................. 2,648 * 2,648 0 *
Michael Epstein................................ 5,296 * 5,296 0 *
Samantha Epstein IRR Trust..................... 1,059 * 1,059 0 *
Marshall Ezralow IRA........................... 5,296 * 5,296 0 *
Investment Management Inc...................... 10,088 * 10,088 0 *
FBR Venture Capital Managers, Inc.............. 56,590 * 56,590 0 *
Robert Feinstein............................... 6,355 * 6,355 0 *
Kenneth O. Frederick........................... 2,648 * 2,648 0 *
Emanuel Friedman............................... 6,355 * 6,355 0 *
Grass Roots Investment Fund.................... 2,648 * 2,648 0 *
Robert Hartheimer.............................. 1,059 * 1,059 0 *
David Hilal.................................... 662 * 662 0 *
Richard Horstmann.............................. 1,059 * 1,059 0 *
Karfunkel Family Foundation.................... 10,591 * 10,591 0 *
Kettle Family, L.P............................. 10,591 * 10,591 0 *
James Kleeblatt................................ 530 * 530 0 *

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Lerner Family Foundation, Inc.................. 10,591 * 10,591 0 *
Kenneth Logue.................................. 1,589 * 1,589 0 *
Walter & Delaney Lundberg...................... 1,059 * 1,059 0 *
John F. Mangan, Jr. ........................... 1,589 * 1,589 0 *
Mario M. Morino Trust.......................... 10,591 * 10,591 0 *
Robert J. Martin............................... 662 * 662 0 *
Milloy Family Technology Partnership, L.P...... 4,236 * 4,236 0 *
Dominic Ng..................................... 1,059 * 1,059 0 *
B.F. Saul Company Employees' Profit Sharing
Retirement Trust............................. 21,183 * 21,183 0 *
Raymond Rice................................... 1,589 * 1,589 0 *
Suzanne Richardson............................. 3,707 * 3,707 0 *
RJA Property Company, LLC...................... 702 * 702 0 *
RNR, LLC....................................... 29,126 * 29,126 0 *
Riyad & Madeleine Said......................... 794 * 794 0 *
Thomas Scott................................... 5,296 * 5,296 0 *
Alan Shusterman................................ 2,118 * 2,118 0 *
Cal Simmons.................................... 10,591 * 10,591 0 *
Gordon V. and Helen C. Smith Foundation........ 10,591 * 10,591 0 *
South Ferry #2, L.P............................ 42,365 * 42,365 0 *
Charles Vance.................................. 21,183 * 21,183 0 *
Edward Wheeler................................. 794 * 794 0 *
Wolfson Equities L.P........................... 10,591 * 10,591 0 *
Gregory M. Wong................................ 993 * 993 0 *
WR&F Associates IV Pool 2(5)................... 6,355 * 6,355 0 *
Bruce Joseph................................. 529 * 529 0 *
John Wyss.................................... 529 * 529 0 *
James Wallace................................ 1,062 * 1,062 0 *
Richard Bodorff.............................. 529 * 529 0 *
Richard McConnell............................ 529 * 529 0 *
William Baker................................ 529 * 529 0 *
Bert Rein.................................... 1,061 * 1,061 0 *
John Bartlett................................ 529 * 529 0 *
Fred Fielding................................ 529 * 529 0 *
Walter Andrew................................ 529 * 529 0 *
Alan L. & Irene V. Wurtzel Revocable Trust..... 2,648 * 2,648 0 *
Peter T. Young................................. 1,059 * 1,059 0 *
Gene Riechers.................................. 40,893 * 40,893 0 *
Hooks Johnston................................. 26,203 * 26,203 0 *
Scott Frederick................................ 6,551 * 6,551 0 *
Harry Weller................................... 6,551 * 6,551 0 *
Alvin L. Ring.................................. 181,819 * 139,991 41,828 *
Spencer Kravitz(6)............................. 372,390 * 286,720 85,670 *
Jay Moskowitz(6)............................... 372,939 * 287,143 85,796 *
Bruce Laskin(7)................................ 70,853 * 54,553 16,300 *
Michael Druckman............................... 10,985 * 8,458 2,527 *
Alan Kuritsky.................................. 1,647 * 1,268 379 *
America Online................................. 61,235 * 61,235 0 *
Monsoon Ventures LLC........................... 129,578 * 129,578 0 *
Monsoon Management Inc. ....................... 47,366 * 47,366 0 *
Chemical Investments, Inc. .................... 8,711 * 8,711 0 *
Sandra Laskin, as Custodian for Michael Jacob
Laskin....................................... 300 * 300 0 *

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Sandra Laskin, as Custodian for David Laskin... 300 * 300 0 *
Rhonda Greenstein Kravitz, as Custodian for
Evan Kravitz................................. 599 * 599 0 *
Rhonda Greenstein Kravitz, as Custodian for
Ariel Kravitz................................ 599 * 599 0 *
Leonard Fremont................................ 60 * 60 0 *
Debbie Moskowitz, as Custodian for Erik
Moskowitz.................................... 300 * 300 0 *
Debbie Moskowitz, as Custodian for Leah
Danielle..................................... 300 * 300 0 *
U.S. Information Technology No. 2 Investment
Enterprise Partnership....................... 54,082 * 48,272 5,810 *
Atlas Venture Fund II, L.P. ................... 123,280 * 110,035 13,345 *
Commonwealth Capital Ventures.................. 67,755 * 60,477 7,278 *
OneLiberty Fund III, L.P. ..................... 24,488 * 21,858 2,630 *
Gilde International B.V. ...................... 202 * 181 21 *
Adams Harkness & Hill Partner Fund............. 7,261 * 6,482 779 *
Robert Davoli and Eileen McDonagh.............. 4,908 * 4,382 526 *
Robert Davoli.................................. 924 * 825 99 *
Gardner Hendrie................................ 8,217 * 7,336 881 *
Robert Badavas................................. 9,625 * 8,592 1,033 *
Thomas R. Holler............................... 1,282 * 1,145 137 *
William J. Reich............................... 482 * 431 51 *
William C. Poellmitz........................... 482 * 431 51 *

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* Less than 1%.

(1) Assuming none of the shares covered by another prospectus are sold. The
other prospectus covers the sale of the following amount of shares for each
of the following selling stockholders:

SELLING STOCKHOLDERS SHARES OF COMMON STOCK
-------------------- ----------------------

Alvin L. Ring........................................... 17,990
Spencer Kravitz......................................... 36,847
Jay Moskowitz........................................... 36,902
Bruce Laskin............................................ 7,011
Michael Druckman........................................ 1,087
Alan Kuritsky........................................... 163

(2) These shares are in addition to the shares covered by another prospectus as
set forth in footnote 1.

(3) Assuming all of the shares covered by this prospectus are sold.

(4) CNF Investments LLC currently owns all of the 42,365 shares of common stock
shown as being held by it. From time to time, CNF Investments LLC may
distribute a portion or all of its shares to the four selling stockholders
identified below CNF Investments LLC, and the number of shares shown
opposite each such name is the maximum number of shares that might be
distributed to such person and the maximum number of shares that may be
offered by them under this prospectus.

(5) WR&F Associates IV Pool 2 currently owns all of the 6,355 shares of common
stock shown as being held by it. From time to time, WR&F Associates IV Pool
2 may distribute a portion or all of its shares to the 10 selling
stockholders identified below WR&F Associates IV Pool 2, and the number of
shares shown opposite each such name is the maximum number of shares that
might be distributed to such person and the maximum number of shares that
may be offered by them under this prospectus.

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(6) Spencer Kravitz and Jay Moskowitz have each agreed not to sell or otherwise
transfer the shares registered under this registration statement and another
registration statement, until the dates and in the amounts indicated below:

OCTOBER 1, JAN. 1, APRIL 1, JULY 1, OCTOBER 1,
2001 2002 2002 2002 2002
---------- ------- -------- ------- ----------

Kravitz.............................. 53,928 53,928 53,928 53,928 53,927
Moskowitz............................ 54,007 54,008 54,007 54,008 54,007

As of the date of this prospectus, Spencer Kravitz and Jay Moskowitz may
sell 53,298 shares and 54,008 shares, respectively, of the aggregate number
of shares registered under this registration statement and another
registration statement.

(7) Bruce Laskin has agreed not to sell or otherwise transfer shares registered
under this registration statement and another registration statement, except
that as of the date of this prospectus 15,391 shares will be eligible for
sale; 15,391 shares will be eligible for sale on October 1, 2001; 15,391
shares will be eligible for sale on January 1, 2002; and 15,391 shares will
be eligible for sale on April 1, 2002.

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PLAN OF DISTRIBUTION

We have been advised that the selling stockholders (and their pledgees,
donees, transferees and other successors in interest) may offer shares of common
stock from time to time depending on market conditions and other factors, in one
or more transactions on the Nasdaq National Market, or any other national
securities exchanges or over-the-counter markets on which the shares may be
traded, or in negotiated transactions, at market prices prevailing at the time
of sale, at prices related to those market prices, at negotiated prices or at
fixed prices.

Sales of shares of common stock by the selling stockholders may involve (i)
block transactions in which the broker or dealer so engaged will attempt to sell
the shares as agent but may position and resell a portion of the block as
principal to facilitate the transaction, (ii) purchases by a broker-dealer as
principal and resale by such broker-dealer for its own account pursuant to this
prospectus, (iii) ordinary brokerage transactions and transactions in which a
broker solicits purchasers or (iv) privately negotiated transactions. To the
extent required, this prospectus may be amended and supplemented from time to
time to describe a specific plan of distribution. In connection with the
distribution of the shares of common stock or otherwise, the selling
stockholders may enter into hedging transactions with broker-dealers. In
connection with such transactions, broker-dealers may engage in short sales of
the common stock in the course of hedging the position they assume with the
selling stockholders. The selling stockholders may also sell the common stock
short and redeliver the shares to close out such short positions.

The selling stockholders may also enter into option transactions (including
call or put option transactions) or other transactions with broker-dealers which
require delivery to such broker-dealer of shares offered hereby, which shares
such broker-dealer may resell pursuant to this prospectus (as supplemented or
amended to reflect such transaction, if necessary). The selling stockholders may
also pledge shares to a broker-dealer and, upon a default, such broker-dealer
may effect sales of the pledged shares pursuant to this prospectus (as
supplemented or amended to reflect such transaction, if necessary). The selling
stockholders may also sell the common stock through one or more underwriters on
a firm commitment or best-efforts basis (with a supplement or amendment to this
prospectus, if necessary). In addition, any shares that qualify for sale
pursuant to Rule 144 may be sold under Rule 144 rather than pursuant to this
prospectus.

Brokers and dealers may receive compensation in the form of concessions or
commissions from the selling stockholders and/or purchasers of shares for whom
they may act as agent and/or to whom they may sell as principal (which
compensation may be in excess of customary commissions). The selling
stockholders and any broker or dealer that participates in the distribution of
shares may be deemed to be underwriters and any commissions received by them and
any profit on the resale of shares positioned by a broker or dealer may be
deemed to be underwriting discounts and commissions under the Securities Act. We
have agreed to indemnify the selling stockholders, the officers, directors,
partners, agents and employees of the selling stockholders, any underwriter (as
defined in the Securities Act) for such selling stockholder, and each person, if
any, who controls such selling stockholder or underwriter within the meaning of
the Securities Act or the Exchange Act against certain liabilities, including
liabilities arising under the Securities Act or the Exchange Act. The selling
stockholders may agree to indemnify any agent or broker-dealer that participates
in transactions involving sales of the shares of common stock against certain
liabilities, including liabilities arising under the Securities Act.

We have advised the selling stockholders that Regulation M under the
Exchange Act may apply to sales of shares and to the activities of the selling
stockholders or broker-dealers in connection therewith. We will bear all costs,
expenses and fees in connection with the registration of the shares of common
stock covered by this prospectus. The selling stockholders will bear any
brokerage commissions and similar selling expenses, if any, attributable to the
sale of the shares.

The selling stockholders may also sell shares under Rule 144 under the
Securities Act, if available, rather than under this prospectus.

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LEGAL MATTERS

The validity of the common stock offered hereby will be passed upon for
Aether by Wilmer, Cutler & Pickering, Washington, D.C.

EXPERTS

The consolidated financial statements and schedule of Aether Systems, Inc.
as of December 31, 1999 and 2000, and for each of the years in the three-year
period ended December 31, 2000, have been incorporated by reference herein and
in the registration statement in reliance upon the reports of KPMG LLP,
independent certified public accountants, which as to the year 2000, is based in
part on the report of Ernst & Young, independent auditors. These reports,
incorporated by reference herein, are given upon the authority of said firms as
experts in accounting and auditing.

The financial statements of LocusOne Communications, Inc. as of December
31, 1998 and 1999, and for each of the years then ended have been incorporated
by reference in this prospectus and elsewhere in the registration statement in
reliance upon the report of KPMG LLP, independent certified public accountants,
incorporated by reference herein, and upon the authority of said firm as experts
in accounting and auditing.

The financial statements of Riverbed Technologies, Inc. as of December 31,
1998 and 1999, and for the period from October 21, 1998 (date of inception) to
December 31, 1998 and for the year ended December 31, 1999, have been
incorporated by reference in this prospectus and elsewhere in the registration
statement in reliance upon the report of KPMG LLP, independent certified public
accountants, incorporated by reference herein, and upon the authority of said
firm as experts in accounting and auditing.

The financial statements of Mobeo, Inc. as of December 31, 1997 and 1998
and for each of the three years in the period ended December 31, 1998 have been
incorporated by reference in this prospectus and elsewhere in the registration
statement in reliance on the report of PricewaterhouseCoopers LLP, independent
accountants, given on the authority of said firm as experts in auditing and
accounting.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Securities Exchange
Act and we file reports, proxy and information statements and other information
with the SEC. You may read and copy all or any portion of the reports, proxy and
information statements or other information we file at the SEC's principal
office in Washington, D.C., and copies of all or any part thereof may be
obtained from the Public Reference Section of the SEC, 450 Fifth Street, N.W.,
Washington, D.C. 20549, and at the SEC's regional offices located at Citicorp
Center, 500 West Madison Street, Suite 1400, Chicago, Illinois 60661 and at 7
World Trade Center, 13th Floor, New York, New York 10048 after payment of fees
prescribed by the SEC. Please call the SEC at 1-800-SEC-0330 for further
information on operation of the public reference rooms. The SEC also maintains a
Web site which provides online access to reports, proxy and information
statements and other information regarding registrants that file electronically
with the SEC at the address http://www.sec.gov.

We have filed with the SEC a Registration Statement on Form S-3 under the
Securities Act with respect to the common stock to be sold in this offering.
This prospectus does not contain all of the information set forth in the
Registration Statement and the exhibits to the Registration Statement. For
further information with respect to Aether and our common stock offered hereby,
reference is made to the Registration Statement and the exhibits filed as a part
of the Registration Statement. Statements contained in this prospectus
concerning the contents of any contract or any other document are not
necessarily complete; reference is made in each instance to the copy of such
contract or any other document filed as an exhibit to the Registration
Statement. Each such statement is qualified in all respects by such reference to
such exhibit. The Registration Statement, including exhibits thereto, may be
inspected without charge at the locations described above, or obtained upon
payment of fees prescribed by the SEC.

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The Securities and Exchange Commission also allows Aether to "incorporate
by reference" information into this prospectus. This means that Aether can
disclose important information to you by referring you to another document filed
separately with the Securities and Exchange Commission. The information
incorporated by reference is considered to be part of this prospectus, except
for any information that is superseded by information that is included directly
in this document, or any future filings with the Securities and Exchange
Commission made under Sections 13(a), 13(c), 14 or 15(d) of the Securities
Exchange Act of 1934.

This prospectus incorporates by reference the documents listed below:

- Aether's Annual Report on Form 10-K, as amended, for the fiscal year
ended December 31, 2000.

- Aether's Current Report on Form 8-K/A filed April 16, 2001, including any
amendments.

- Aether's Current Report on Form 8-K filed May 11, 2001.

- Aether's Current Report on Form 8-K filed June 29, 2001.

- Aether's Quarterly Report on Form 10-Q for the quarter ended March 31,
2001.

- Aether's Proxy Statement on Schedule 14A dated May 25, 2001.

- The financial statements of LocusOne Communications and Riverbed
Technologies included in Aether's Registration Statement on Form S-1
(File No. 333-44566), as amended.

- The Description of Capital Stock contained in Aether's Registration
Statement on Form S-1 (Registration No. 333-45656) dated September 27,
2000, including any amendments or reports filed for the purpose of
updating such description.

- In addition, all documents subsequently filed by Aether pursuant to
Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the
termination of the offering shall be deemed to be incorporated by
reference herein from their respective dates of filing.

You may request a copy of any filings incorporated by reference in this
prospectus from Aether by contacting:

Kevin Connelly
VP Finance and Accounting
Aether Systems, Inc.
11460 Cronridge Drive
Owings Mills, Maryland 21117
Telephone: (410) 654-6400

You should rely only on the information incorporated by reference or
provided in this prospectus. Aether has not authorized anyone else to provide
you with different or additional information. You should not assume that the
information in this prospectus is accurate as of any date other than the date
set forth on the front cover.

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2,881,980 SHARES

[AETHER LOGO]

COMMON STOCK

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PROSPECTUS
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JULY 31, 2001

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