Document:

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                                                                   Exhibit 10.20
                                                       Employment Agreement with
                                                                  Peter Aronstam

                                           {Letterhead of Airspan Networks Inc.}

Feb. 15, 2001

Peter Aronstam
2840 N.W. 49/th/ Street
Boca Raton, FL 33434

Dear Peter,

It is a pleasure to provide this formal offer to you for the position of Senior
Vice President and Chief Financial Officer ("CFO") of Airspan Networks Inc.
("Airspan" or the "Company"). Both the Board of Directors ("Board") of Airspan
and I are enthusiastic about having you join us in this crucial role. The
position of CFO reports directly to me, will be based at the Airspan offices in
Sunrise, Florida and will require close collaboration with the worldwide Airspan
team.

Here are the detailed terms and conditions of this offer:

1.   Salary

     Your starting base salary will be US$260,000 per year, to be paid twice per
     month. The salary will be subject to periodic review and adjustment by the
     Board.

2.   Incentive Compensation

     You will be eligible for incentive compensation in accordance with
     Airspan's bonus compensation plan in effect from time to time. A copy of
     the plan for 2001 is attached as Schedule 1 hereto. The 2001 plan provides
     an on-target bonus for the CFO position of 50% of the base salary. The
     actual bonus value for 2001 will be determined at the conclusion of the
     full year 2001 and will include a Corporate Performance Factor and an
     individual Performance Factor, which will vary from 0 to 200% of the target
     50%.

3.   Stock Grant

     On the first day of your employment with Airspan, Airspan will grant to you
     an option for the purchase of 325,000 shares of Airspan's common stock. The
     options will be granted under Airspan's 1998 Stock Option and Restricted
     Stock Plan as amended (the "Plan"), and will be subject to the provisions
     of the Plan unless otherwise stated in this offer. The options so granted
     will be exercisable in accordance with the Plan, at a price equal to the
     closing market price for the common stock of Airspan as of the first day of
     your employment. Twenty-five percent (25%) of the options will vest on the
     first anniversary of your employment, and the remaining seventy-five
     percent (75%) thereafter monthly over the next three years of your
     employment.

     In addition to this initial grant of options, you will be eligible for
     grants of additional options as may be determined by the Board in future
     under the Plan.
<PAGE>

4.   Employee Benefits

     You will be eligible to participate in the Company's benefit plans and to
     receive the benefits that the Company customarily makes available to its
     employees in a position comparable to yours. You will be entitled to three
     weeks of vacation per year plus customary holidays.

5.   Employment Security

     a) If the Company terminates your employment other than for "Cause" or if
     you terminate your employment with "Good Reason", you will be entitled to a
     separation payment, to be payable over a twelve month period following such
     termination, equal to twelve months of your base salary as of the date of
     your termination.

     "Cause" means (a) your material breach of this agreement or any other
     agreement between the Company and you which has not been cured within a
     reasonable period after you shall have received notice of such breach from
     the Company, (b) your failure to follow the direction of the board of
     directors, which directions are in compliance with all applicable laws, and
     the you have not cured such failure within a reasonable period after you
     shall have received notice of such breach from the Company, (c) your
     conviction of a crime involving fraud or theft or that constitutes a
     felony, (d) your engagement of serious willful misconduct that is
     materially injurious to the Company, or (e) your willful failure to perform
     the duties and responsibilities of your position.

     "Good Reason" means (a) a material diminution of your duties, authority or
     responsibilities, (b) your removal from the position of Senior Vice
     President and Chief Financial Officer of the Company, (c) a material
     reduction of your annual base salary, or (d) a breach by the Company of any
     material term of this agreement or any other agreement between the Company
     and you which has not been cured within a reasonable period after you shall
     have given the Company notice of such breach.

     This provision will not alter the at-will status of your employment.

     b) If there is a "Change of Control" of the Company, and within one year of
     the effective date thereof either (i) the Company terminates your
     employment, or (ii) you voluntarily terminate your employment because
     either you are required to relocate from the Sunrise, Florida offices of
     the Company or your duties and responsibilities are changed in a material
     way, you will be entitled to receive employment security of twelve months
     of the total cash compensation that would have been payable to you in the
     twelve-month period following such termination. Such compensation will
     include all bonuses that would have been payable (including all bonuses in
     connection with the end of the fiscal year of the Company during such
     twelve-month period and the pro-rated portion of any bonus that would have
     been payable for the following year at the same percentage of
     compensation). You will also be entitled during that twelve-month period to
     the benefits described in Section 4 above.

     "Change of Control" means any of the following: (a) the acquisition by any
     person, entity or "group" (as defined in Section 13(d) of the Securities
     Exchange Act of 1934, as amended), other than the Principal Shareholders
     (as defined below) of 35% or more of the combined voting power of the
     Company's then outstanding voting securities; (b) the merger,
     consolidation, acquisition or other transaction of the Company as a result
     of which the Principal Shareholders do not own, directly or indirectly,
     more than 50% of the combined voting power entitled to vote generally in
     the election of the board of directors of the Company, or, as applicable,
     the acquirer, successor or surviving entity; (c) the liquidation or
     dissolution of the Company; (d) the sale, transfer or other disposition of
     all or substantially all of the assets of the Company, whether in a single
     transaction or in a series of transactions, to one more persons or entities
     that are, immediately prior to and after such sale, transfer or
     disposition, persons or entities in which the Principal Shareholders do not
     own, directly or indirectly, more than 50% of the combined voting power
     entitled to vote
<PAGE>

     generally in the election of the board of directors of such persons or
     entities; and (e) a "change of control" under any material document or
     instrument governing the indebtedness of the Company.

     "Principal Shareholders" means any or all of those persons or entities
     (other than officers of the Company who were not on the board of directors
     of the Company) who (a) owned, directly or indirectly, as of July 19, 2000,
     more than 75% of the combined voting power entitled to vote generally in
     the election of the board of directors of the Company at such date, and (b)
     are entities, which, directly or indirectly, are in control of, controlled
     by or under common control with, any of the persons or entities described
     in clause (a).

     c) If your employment is terminated in the circumstances contemplated by
     paragraphs a) or b) of this Section 5, any options which you have been
     granted in accordance with Section 3 above and which have not yet vested in
     you in accordance with the Plan will immediately vest in you.

     d) If the Company terminates your employment for Cause, or if you
     voluntarily terminate your employment without Good Reason, then any options
     granted to you under the Plan that have not vested on or prior to the date
     of termination will expire.

6.   Confidentiality

     On or before the first day of your employment, you will be required to sign
     and abide by the Confidentiality and Proprietary Information Agreement
     attached hereto as Schedule 2.

Under federal immigration laws, the Company is required to verify your identity
and legal authority to work in the United States. Accordingly, please be
prepared to furnish appropriate documents to satisfy those requirements. This
offer is conditioned upon submission of satisfactory documentation.

The terms and conditions set forth in this offer have been authorized and
approved by the Board of Directors of the Company and all other necessary
corporate actions, provided that the actions required to make the stock grant
referred to in section 3 above will be taken no later than five days after you
become an employee of the Company.

If you are in agreement with the terms of this offer, please acknowledge by
signing below. This offer is valid until February 16, 2001.

Sincerely,

/s/  Eric Stonestrom
--------------------
Airspan Networks Inc.

By:  Eric Stonestrom
President and Chief Executive Officer

Agreed and accepted by:

/s/ Peter Aronstam                           Feb. 15, 2001
------------------                           -------------
Peter Aronstam                               Date<PAGE>

                                                                   Exhibit 10.21

                             AIRSPAN NETWORKS INC.

                      2001 SUPPLEMENTAL STOCK OPTION PLAN

     Section 1.  Purpose. The purpose of the Airspan Networks Inc. 2001
                 -------
Supplemental Stock Option Plan (the "Plan") is to promote the interests of
Airspan Networks Inc., a Washington corporation (the "Company"), and any
Subsidiary thereof and the interests of the Company's shareholders by providing
an opportunity to selected Consultants, New-Hires and Non-Officer employees of
the Company or any Subsidiary thereof as of the date of the adoption of the Plan
or at any time thereafter to purchase Common Stock of the Company. By
encouraging such stock ownership, the Company seeks to attract, retain and
motivate such employees and persons and to encourage such employees and persons
to devote their best efforts to the business and financial success of the
Company. It is intended that this purpose will be effected by the granting of
"non-qualified stock options" to acquire the Common Stock of the Company.

     Section 2.  Definitions. For purposes of the Plan, the following terms used
                 -----------
herein shall have the following meanings, unless a different meaning is clearly
required by the context.

     2.1.  "Board of Directors" shall mean the Board of Directors of the
Company.

     2.2.  "Code" shall mean the Internal Revenue Code of 1986, as amended.

     2.3.  "Committee" shall mean the committee of the Board of Directors
referred to in Section 5 hereof.

     2.4   "Consultant" shall be a person who performs services to the Company
on a contract basis and who is not an employee of the Company.

     2.5.  "Common Stock" shall mean the Common Stock, $0.003 par value, of the
Company.

     2.6.  "Eligible Participant" shall mean a Non-Officer Employee, New-Hires
and Consultants of the Company, employed by, or performing services for, the
Company or any Subsidiary of the Company, specifically excluding directors and
officers of the Company.

     2.7.  "New-Hires" shall mean a new employee who, as an inducement essential
to the individual's entering into an employment relationship with the Company,
is to receive Options.

     2.8.  "Non-Qualified Option" shall mean the Options granted to the Eligible
Participant pursuant to the Plan that are intended to be, and qualify as, "non--
qualified stock options" as described in Treasury Regulation Section 1.83--7 or
any successor regulation thereto.
<PAGE>

     2.9.  "Option" shall mean any Non--Qualified Option granted to an Eligible
Participant pursuant to the Plan.

     2.10. "Subsidiary of the Company" shall have the meaning set forth in
            -------------------------
Section 424(f) of the Code.

     Section 3.  Eligibility. Options may be granted to any Eligible
                 -----------
Participant. The Committee shall have the sole authority to select the Eligible
Participant to whom Options are to be granted hereunder. No person shall have
any right to participate in the Plan. Any person selected by the Committee for
participation during any one period will not by virtue of such participation
have the right to be selected as a Participant for any other period.

     Section 4.  Common Stock Subject to the Plan.
                 --------------------------------

     4.1.  Number of Shares. The total number of shares of Common Stock for
           ----------------
which Options may be granted under the Plan shall be determined by the
Committee, in consultation with the Board of Directors, so long as such shares
of Common Stock subject to such Options may be validly issued upon exercise
pursuant to applicable laws.

     4.2.  Reissuance. The shares of Common Stock that may be subject to Options
           ----------
granted under the Plan may be either authorized and unissued shares or shares
reacquired at any time and now or hereafter held as treasury stock as the Board
of Directors may determine.

     Section 5.  Administration of the Plan.
                 --------------------------

     5.1.  Administration. The Plan shall be administered by a committee of the
           --------------
Board of Directors (the "Committee") established by the Board of Directors and
consisting of no less than two persons.

     5.2.  Grant of Options.
           ----------------

     (a)   Options. The Committee shall have the sole authority and discretion
           -------
under the Plan (i) to select the Eligible Participants who are to be granted
Options hereunder so long as such Eligible Participants meet the requirements
set forth in the definition of Eligible Participants set forth in this Plan;
(ii) to establish the number of shares of Common Stock that may be issued under
each Option; (iii) to determine the time and the conditions subject to which
Options may be exercised in whole or in part; (iv) to determine the form of the
consideration that may be used to purchase shares of Common Stock upon exercise
of any Option (including the circumstances under which the Employee may pay all
or part of the exercise price by entering into a promissory note with the
Company, or circumstances under which the Company's issued and outstanding
shares of Common Stock may be used by a Participant to exercise an Option); (v)
to impose restrictions and/or conditions with respect to shares of Common Stock
acquired upon exercise of an Option; (vi) to determine the circumstances under
which shares of Common Stock acquired upon exercise of any Option may be subject
to repurchase by the Company; (vii) to establish a vesting provision for any
Option relating to the time
<PAGE>

when (or the circumstances under which) the Option may be exercised by a
Participant, including, without limitation, vesting provisions that may be
contingent upon (A) the Company meeting specified financial goals, (B) a change
of control of the Company or (C) the occurrence of other specified events;
(viii) to accelerate the time when outstanding Options may be exercised; and
(ix) to establish any other terms, restrictions and/or conditions applicable to
any Option not inconsistent with the provisions of the Plan.

     5.3.  Interpretation. The Committee shall be authorized to interpret the
           --------------
Plan and may, from time to time, adopt such rules and regulations, not
inconsistent with the provisions of the Plan, as it may deem advisable to carry
out the purposes of the Plan.

     5.4.  Finality. The interpretation and construction by the Committee of any
           --------
provision of the Plan, any Option granted hereunder or any agreement evidencing
any such Option shall be final and conclusive upon all parties.

     5.5.  Voting. Members of the Committee may vote on any matter affecting the
           ------
administration of the Plan or the granting of Options under the Plan.

     5.6.  Expenses, Etc. All expenses and liabilities incurred by the Committee
           --------------
in the administration of the Plan shall be borne by the Company. The Committee
may employ attorneys, consultants, accountants or other persons in connection
with the administration of the Plan. The Company, and its officers and
directors, shall be entitled to rely upon the advice, opinions or valuations of
any such persons.

     5.7.  Indemnification. Neither the members of the Board of Directors nor
           ---------------
any member of the Committee shall be liable for any act, omission, or
determination taken or made in good faith with respect to the Plan or any
Options granted under it, and members of the Board of Directors and the
Committee shall be entitled to indemnification and reimbursement by the Company
in respect of any claim, loss, damage, or expense (including attorneys' fees,
the costs of settling any suit, provided such settlement is approved by
independent legal counsel selected by the Company, and amounts paid in
satisfaction of a judgment, except a judgment based on a finding of bad faith)
arising therefrom to the full extent permitted by law.

     Section 6.  Terms and Conditions of Options.
                 -------------------------------

     6.1.  Non-Qualified Options. The terms and conditions of each Option
           ---------------------
granted under the Plan, which shall be a Non-Qualified Option, shall be
specified by the Committee, in its sole discretion, and shall be set forth in a
written option agreement between the Company and the Participant in such form as
the Committee shall approve. The terms and conditions of each Non-Qualified
Option will be such (and each Non-Qualified Option Agreement shall expressly so
state) that each Non-Qualified Option issued hereunder shall not constitute nor
be treated as an "incentive stock option" as defined in Section 422(b) of the
Code but will be a "non-qualified stock option" for Federal, state and local
income tax purposes. The terms and conditions of any Option
<PAGE>

granted hereunder need not be identical to those of any other Non-Qualified
Option granted hereunder.

     The terms and conditions of each Non-Qualified Option Agreement shall
include the following:

     (a)  The option (exercise) price shall be fixed by the Committee and may be
equal to, more than or less than 100% of the fair market value of the shares of
Common Stock subject to the Non-Qualified Option on the date such Non-Qualified
Option is granted, provided, however, that the option (exercise) price shall not
                   --------  -------
be less than the par value of such shares of Common Stock.

     (b)  The Committee shall fix the term of all Options granted pursuant to
the Plan (including the date on which such Option shall expire and terminate).
Each Option shall be exercisable in such amount or amounts, under such
conditions (including provisions governing the rights to exercise such Option),
and at such times or intervals or in such installments as shall be determined by
the Committee in its sole discretion.

     (c)  Except as otherwise provided in an individual Option Agreement,
Options shall not be transferable otherwise than by will or the laws of descent
and distribution, or a domestic relations order, and during a Participant's
lifetime an Option shall be exercisable only by the Participant or an alternate
payee under a domestic relations order.

     (d)  To the extent that the Company is required to withhold any Federal,
state or local taxes in respect of any compensation income realized by any
Participant in respect of an Option granted hereunder or in respect of any
shares of Common Stock acquired upon exercise of an Option, the Company shall
deduct from any payments of any kind otherwise due to such Participant the
aggregate amount of such Federal, state or local taxes required to be so
withheld or, if such payments are insufficient to satisfy such Federal, state or
local taxes, or if no such payments are due or to become due to such
Participant, then, such Participant will be required to pay to the Company, or
make other arrangements satisfactory to the Company (including, with prior
Committee approval, use of a promissory note in favor of the Company) regarding
payment to the Company of, the aggregate amount of any such taxes. All matters
with respect to the total amount of taxes to be withheld in respect of any such
compensation income shall be determined by the Board of Directors in its sole
discretion.

     Section 7.  Adjustments. In the event that, after the adoption of the Plan
                 -----------
by the Board of Directors, the outstanding shares of the Company's Common Stock
shall be increased or decreased or changed into or exchanged for a different
number or kind of shares of stock or other securities of the Company or of
another corporation through reorganization, merger or consolidation,
recapitalization, reclassification, stock split, split-up, combination or
exchange of shares or declaration of any dividends payable in Common Stock, the
Board of Directors shall appropriately adjust the number of shares of Common
Stock (and the option price per share) subject to the unexercised portion of any
outstanding Option (to the nearest possible full share).
<PAGE>

     Section 8.  Effect of the Plan on Employment Relationship. Neither the Plan
                 ---------------------------------------------
nor any Option granted hereunder to an Eligible Participant shall be construed
as conferring upon such Eligible Participant any right to continue in the employ
of (or otherwise provide services to) the Company or any Subsidiary or Parent
thereof, or limit in any respect the right of the Company or any Subsidiary or
Parent thereof to terminate such Eligible Participant's employment or other
relationship with the Company or any Subsidiary or Parent, as the case may be,
at any time.

     Section 9.  Amendment of the Plan. The Committee or Board of Directors may
                 ---------------------
amend or suspend the Plan or any portion thereof at any time, provided such
amendment is made with shareholder approval if such approval is necessary to
comply with any tax or regulatory requirement. The Committee in its sole
discretion may amend the Plan so as to conform with local rules and regulations
subject to any provisions to the contrary specified herein.

     Section 10. Amendment of an Option. In its sole and complete discretion,
                 ----------------------
the Committee may at any time amend any Option for the following reasons: (i)
additions and/or changes to the Code, any federal or state securities law, or
other law or regulations applicable to the Option, are made, and such additions
and/or changes have some effect on the Option, or (ii) any other event not
described in clause (i) occurs and the Eligible Participant gives his or her
consent to such amendment.

     Section 11. Exemption from Computation of Compensation for Other Purposes.
                 -------------------------------------------------------------
By acceptance of an applicable Option, subject to the conditions of such Option,
each Eligible Participant shall be considered in agreement that all shares sold
or awarded and all Options granted under this Plan shall be considered special
incentive compensation and will be exempt from inclusion as "wages" or "salary"
in pension, retirement, life insurance, and other employee benefits arrangements
of the Company, except as determined otherwise by the Company. In addition, each
beneficiary of a deceased Eligible Participant shall be in agreement that all
such Options will be exempt from inclusion in "wages" or "salary" for purposes
of calculating benefits of any life insurance coverage sponsored by the Company.

     Section 12. Listing, Registration and Other Legal Compliance. No Options or
                 ------------------------------------------------
shares of the Common Stock shall be required to be issued or granted under the
Plan unless legal counsel to the Company shall be satisfied that such issuance
or grant will be in compliance with all applicable federal and state securities
laws and regulations and any other applicable laws or regulations. The Committee
may require, as a condition of any payment or share issuance, that certain
agreements, undertakings, representations, certificates, and/or information, as
the Committee may deem necessary or advisable, be executed or provided to the
Company to assure compliance with all such applicable laws or regulations. Any
certificates for shares of Common Stock delivered under the Plan may be subject
to such stock-transfer orders and such other restrictions as the Committee may
deem advisable under the rules, regulations, or other requirements of the
Securities and Exchange Commission, any stock exchange upon which the Common
Stock is then listed, and any applicable federal or state securities law. In
addition, if, at any time specified herein (or in any Agreement or otherwise)
for (a) the making of any Option, or
<PAGE>

the making of any determination, (b) the issuance or other distribution of
Common Stock, or (c) the payment of amounts to or through an Eligible
Participant with respect to any Option, any law, rule, regulation, or other
requirement of any governmental authority or agency shall require the Company,
any affiliate, or any Eligible Participant (or any estate, designated
beneficiary, or other legal representative thereof) to take any action in
connection with any such determination, any such shares to be issued or
distributed, any such payment, or the making of any such determination, as the
case may be, shall be deferred until such required action is taken.

     Section 13.  Rights as Shareholder. No Eligible Participant or beneficiary
                  ---------------------
shall be deemed a shareholder of the Company nor have any rights as such with
respect to any shares to be provided under the Plan until he or she has become
the holder of such shares.

     Section 14.  Construction of the Plan. The Plan, and its rules, rights,
                  ------------------------
agreements and regulations, shall be governed, construed, interpreted and
administered solely in accordance with the laws of the state of Washington. In
the event any provision of the Plan shall be held invalid, illegal or
unenforceable, in whole or in part, for any reason, such determination shall not
affect the validity, legality or enforceability of any remaining provision,
portion of provision or the Plan overall, which shall remain in full force and
effect as if the Plan had been absent the invalid, illegal or unenforceable
provision or portion thereof

     Section 15.  Termination of the Plan. The Board of Directors may terminate
                  -----------------------
the Plan at any time. Unless the Board of Directors shall theretofore have
terminated the Plan, the Plan shall terminate ten years after the date of its
initial adoption by the Board of Directors. No Option may be granted hereunder
after termination of the Plan. The termination or amendment of the Plan shall
not alter or impair any rights or obligations under any Option theretofore
granted under the Plan.

     Section 16.  Effective Date of the Plan. The Plan shall be effective as of
                  --------------------------
February 7, 2001, the date on which the Board of Directors of the Company
adopted the Plan.

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