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                                                                    EXHIBIT 10.5


                    MacDONALD, DETTWILER AND ASSOCIATES LTD.
                      1999 STOCK OPTION AND INCENTIVE PLAN

1.     PURPOSE OF THE PLAN

The purpose of this 1999 Stock Option and Incentive Plan is to advance the
interests of MacDonald, Dettwiler and Associates Ltd. ("MDA or "COMPANY") and
its shareholders by enabling MDA and other Participating Companies (as defined
below) to attract and retain highly talented employees, officers and directors
and, subject to applicable laws, consultants, who are in a position to make
significant contributions to the success of MDA, to reward them for their
contributions to the success of MDA, and to encourage them, through share
ownership, to increase their proprietary interest in MDA and their personal
interest in its continued success and progress.

This 1999 Stock Option and Incentive Plan provides for the award of MDA stock
options to acquire MDA common shares.

2.     DEFINITIONS

For the purposes of this Plan and related documents, the following definitions
apply:

       "ACT" means the Canada Business Corporations Act, as amended.

       "AFFILIATE" has the meaning specified in the Act.

       "AWARD AGREEMENT" means the stock option agreement or other written
       agreement between MDA and a Grantee that evidences and sets out the terms
       and conditions of a Grant.

       "BOARD" means the Board of Directors of the Company.

       "CAI ENTITIES" Means CAI Capital Partners and Company II, L.P., CAI
       Partners and Company II, L.P., and CAI Capital Partners and Company II-C,
       L.P.

       "COMMITTEE" means a committee of the Board designated from time to time
       by resolution of the Board, which committee shall consist of no fewer
       than two members of the Board, none of whom shall be an officer or other
       salaried employee of any Participating Company.

       "COMPANY" or "MDA" means MacDonald, Dettwiler and Associates Ltd., a
       corporation governed by the laws of Canada or any successor thereof.

       "EFFECTIVE DATE" means December 22, 1999.

       "EMPLOYEE" with respect to a Participating Company means an individual
       who is considered an employee of the Participating Company as defined
       under the Income Tax Act, (Canada) as amended, or who is an individual
       who is a full-time or a part-time


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       dependent contractor of the Participating Company providing services
       normally provided by an employee of the Participating Company and is
       subject to the same control and direction by the Participating Company
       over the detail and methods of work as an employee of the Participating
       Company.

       "FAIR MARKET VALUE OF A SHARE" Means the closing sale price of the Shares
       on the national securities or stock exchange on which the Shares are then
       principally traded or, if that measure of price is not available, in a
       national market system for securities on the date of the Grant (or such
       other date as is specified herein). In the event that there are no sales
       of Shares on any such exchange or market on date of the Grant (or such
       other date as is specified herein), the fair market value of Shares on
       the date of the Grant (or such other date as is specified herein) shall
       be deemed to be the closing sale price on the next preceding day on which
       Shares were sold on any such exchange or market. In the event that the
       Shares are not listed on any such market or exchange on the applicable
       date, a valuation of the fair market value of a Share on such date shall
       be made by the Board in its sole discretion.

       "GRANT" Means an award of an Option under the Plan.

       "GRANTEE" means a person who receives or holds an Option under the Plan.

       "OPTION" Means an option to acquire Shares granted under the Plan.

       "OPTION TERMINATION DATE" is defined in Section 9(b) below.

       "PARTICIPATING COMPANY" means the Company and any Affiliate of the
       Company prior to such event and, following a public offering, means the
       Company and any Subsidiary of the Company.

       "PERSON" shall mean an individual, corporation, partnership, association
       or other person or entity, or any group of two or more of the foregoing
       that have agreed to act together.

       "PLAN" means this 1999 Stock Option and Incentive Plan.

       "SECURITIES LAWS" means all applicable laws, rules, regulations, rules,
       orders, and published policies relating in full or in part to trading in
       securities, to the extent legally enforceable.

       "SHAREHOLDERS AGREEMENT" Means the unanimous shareholders' agreement
       dated December 22, 1999 among the CAI Entities, 597858 B.C. Ltd., as
       agent, Orbital Sciences Corporation and those persons who become parties
       thereto and bound thereto from time to time.

       "SHARES" means common shares in the capital of the Company.

       "SUBSIDIARY" has the meaning specified in the Act.


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       "TERMINATING TRANSACTION" Means any of the following events: (a) the
       dissolution or liquidation of the Company; (b) a reorganization, merger,
       amalgamation or consolidation of the Company with one or more other
       Persons as a result of which the Company goes out of existence or becomes
       a Subsidiary of a corporation other than a Participating Company
       immediately prior to such event or there has otherwise been an
       acquisition of control of the Company (within the meaning of the Income
       Tax Act (Canada)) by a Person other than a Participating Company
       immediately prior to such event and other than pursuant to the exercise
       of rights under the Treasury Option Agreement or the Secondary Option
       Agreement (each as defined in the Shareholders' Agreement) or (c) a sale
       of all or substantially all of the Company's assets to a Person or entity
       other than a Person that was a Participating Company immediately prior to
       such event; or (d) a sale to one Person (or two or more Persons acting in
       concert), other than to a Participating Company immediately prior to such
       event, of equity securities of the Company resulting in such Person or
       Persons holding Shares representing at least eighty percent (80%) or more
       of the aggregate voting power of all outstanding equity securities of the
       Company.

       "TOTAL DISABILITY" means permanent and total disability as determined in
       the sole discretion of the Board.

3.     ADMINISTRATION OF PLAN

       (a)    Administration by Board. The Plan shall be administered by the
              Board. The Board shall have authority, not inconsistent with the
              express provisions of the Plan, to:

              (i)    award Grants consisting of Options to such eligible persons
                     as the Board may select;

              (ii)   determine the timing of Grants and the number of Shares
                     subject to each Grant;

              (iii)  determine the terms and conditions of each Grant, including
                     the nature and duration of any restriction or condition (or
                     provision for lapse thereof) relating to the vesting or
                     forfeiture of a Grant;

              (iv)   adopt such rules and regulations as the Board may deem
                     necessary or appropriate to carry out the purposes of the
                     Plan; and

              (v)    interpret the provisions of the Plan and of any Grants made
                     hereunder and decide any questions and settle all
                     controversies and disputes that may arise in connection
                     with the Plan.

              All decisions, determinations, interpretations or other actions by
              the Board with respect to the Plan shall be final, conclusive and
              binding on all Persons, including the Company, Participating
              Companies and Grantees and their respective legal representatives,
              their successors in interest and permitted assigns and upon all
              other Persons claiming by, through, under or against any of them.


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       (b)    Administration and Delegation by Committee. Subject to the Act but
              otherwise in its sole discretion, the Board may delegate some of
              its powers with respect to the Plan to a Committee (in which case
              references to the Board in this Plan shall be deemed to refer to
              the Committee, where appropriate) except for the authority to make
              Grants under the Plan. The delegated authority shall include the
              power to:

              (i)    determine the timing of Grants and the number of Shares
                     subject to each Grant; and

              (ii)   determine the terms and conditions of each Grant, including
                     the nature and duration of any restriction or condition (or
                     provision for lapse thereof) relating to the vesting or
                     forfeiture of a Grant.

4.     SHARES SUBJECT TO THE PLAN

       (a)    Availability. Subject to adjustment as provided in Section 4(c)
              below, the maximum aggregate number of Shares available for
              issuance under the Plan will be six (6) million. The number of
              Shares that may be so reserved and authorized for issuance to any
              one person shall not exceed 5 percent of the total issued and
              outstanding Shares of the Company (calculated on a non-diluted
              basis).

       (b)    Reavailability of Options; Shares to be Delivered. If any Shares
              covered by a Grant are not purchased or are forfeited, or if a
              Grant otherwise terminates without delivery of any Shares subject
              thereto, then the number of Shares so terminated or forfeited
              shall again be available for making Grants under the Plan. Shares
              delivered under the Plan shall be authorized but unissued shares.
              No fractional Shares shall be delivered under the Plan.

       (c)    Changes in Capital. In the event of a stock dividend, share split
              or combination of shares, exchange of securities, distribution
              payable in Shares, recapitalization or other change in MDA's
              capital stock, the number and kind of securities subject to Grants
              then outstanding or subsequently awarded under the Plan, the
              exercise price of any outstanding Option, the maximum number of
              Shares that may be delivered under the Plan, and other relevant
              provisions shall be appropriately adjusted by the Board, so that
              the proportionate interest of the Grantee immediately following
              such event shall, to the extent practicable, be the same as
              immediately before such event.

5.     EFFECTIVE DATE

The Plan shall be effective as of the Effective Date.

6.     AWARD AGREEMENT

Each Grant pursuant to the Plan shall be evidenced by an Award Agreement, to be
executed by MDA and by the Grantee, in such form or forms as the Board shall
from time to time approve containing terms and conditions not inconsistent with
the terms and conditions of this Plan.



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7.     OPTION EXERCISE PRICE

The Option exercise price for a Share to be issued under the Plan shall be not
less than the Fair Market Value of a Share on the Grant date, as determined by
the Board in its sole discretion.

8.     DISCRETIONARY OPTION PLAN

Grants may be made under the Plan to any Employee or director or officer of any
Participating Company and, subject to Securities Laws, to individuals while
employed as consultants of any Participating Company, in each case as the Board
shall determine and designate from time to time. The Board may set limits on the
number of Options that may be granted to any Person or class of Persons.

9.     VESTING AND TERMINATION OF OPTIONS

       (a)    Vesting of Discretionary Options. Subject to the other provisions
              of this Section 9, Options granted pursuant to Section 8 shall
              vest and become exercisable at such time and in such instalments
              as the Board shall provide in each individual Award Agreement.
              Notwithstanding the foregoing, the Board may, in its sole
              discretion, accelerate the time at which all or any part of an
              Option may be exercised.

       (b)    Termination of Options. Each Option shall expire and terminate on
              such date as the Board shall determine ("OPTION TERMINATION
              DATE"), which in no event shall be later than ten (10) years from
              the date of the Grant of such Option. Upon termination of an
              Option or portion thereof, the Grantee shall have no further right
              to purchase Shares pursuant to such Option.

       (c)    Termination of Employment, Officership or Directorship. In the
              event of the termination of all positions of employment,
              officership or directorship of a Grantee with the Participating
              Companies for any reason other than for "cause" (pursuant to
              Section 11 below) or by reason of death or Total Disability,
              except as may be provided in any Award Agreement all Options that
              are not exercisable shall terminate on the day after notice of
              termination of such position(s) is given. Options that are
              exercisable on such date shall continue to be exercisable for (A)
              three (3) months following the day notice of termination of such
              position(s) was given or (B) the Option Termination Date,
              whichever occurs first; such longer period (not to exceed three
              (3) years following the day notice of termination of such
              position(s) was given) as may be specified in the Grantee's Award
              Agreement. A Grantee who is an Employee, officer or director of a
              Participating Company shall be deemed to have incurred a
              termination and been given notice of termination for purposes of
              this Section 9(c) if such Participating Company ceases to be a
              Participating Company, unless such Grantee is an Employee, officer
              or director of any other Participating Company.


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       (d)    Rights in the Event of Death. In the event that the employment
              and/or officership and/or directorship of a Grantee with a
              Participating Company is terminated by reason of death, all
              Options that are not exercisable on the day prior to the Grantee's
              death shall terminate on the date of death. Options that were
              exercisable on the date prior to the Grantee's death may be
              exercised by the Grantee's executor or administrator or by the
              Person or Persons to whom the Option is transferred by will or the
              applicable laws of descent and distribution, at any time within
              the one-year period (or such longer period as the Board may
              determine prior to the expiration of such one-year period)
              beginning with the date of the Grantee's death, but in no event
              beyond the Option Termination Date.

       (e)    Rights in the Event of Total Disability. In the event that the
              employment and/or directorship of an Grantee with a Participating
              Company is terminated by reason of Total Disability, all Options
              that are not exercisable shall terminate on the
              employment/officership/directorship termination date. Options that
              were exercisable on the employment/officership/directorship
              termination date may be exercised at any time within the one-year
              period (or such longer period as the Board may determine prior to
              the expiration of such one-year period) beginning with the
              commencement of the Grantee's Total Disability (as determined by
              the Board) but in no event beyond the Option Termination Date.

       (f)    Leave of Absence. An approved leave of absence shall not
              constitute a termination of employment under the Plan. An approved
              leave of absence shall mean an absence approved pursuant to the
              policy of a Participating Company for military leave, sick leave,
              or other bona fide leave, not to exceed ninety (90) days or, if
              longer, as long as the Employee's right to re-employment is
              guaranteed by contract, statute or the policy of a Participating
              Company. Notwithstanding the foregoing, in no event shall an
              approved leave of absence result in an Option surviving beyond the
              Option Termination Date.

10.    EXERCISE OF OPTIONS: NON-TRANSFERABILITY

       (a)    Exercise of Options. Vested Options may be exercised, in whole or
              in part, by giving written notice of exercise to the Company,
              which notice shall specify the number of Shares to be purchased,
              shall be accompanied by payment in full of the purchase price
              therefor in accordance with Section 10(b) below and the full
              amount of any federal, provincial, state and/or withholding and
              other employment taxes applicable to such person as a result of
              such exercise and shall be accompanied by signed copies of the
              document(s) referred to in Section 10(c) below. No Shares shall be
              issued pursuant to the exercise of an Option until full payment of
              the purchase price and applicable withholding tax has been made to
              the Company. Upon receipt of such amounts, the Company shall issue
              forthwith share certificates representing the Shares purchased
              pursuant to the exercise of the Option. Until the share
              certificates representing such Shares have been issued by the
              Company, the Grantee shall have no right to vote or receive
              dividends on or exercise any other rights as a shareholder, with
              respect to optioned Shares notwithstanding the exercise of the
              Option.


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       (b)    Payment. Full payment of the purchase price for the Shares as to
              which an Option is being exercised shall be made in Canadian
              dollars in cash or by cheque in a form satisfactory to the
              Company.

       (c)    Unanimous Shareholders Agreement. The Shares are subject to the
              terms and conditions of the Shareholders' Agreement. It is a
              condition to the exercise of an Option that the Grantee, if not
              already a party to the Shareholders Agreement, at or before the
              time of the exercise of the Option, must sign and deliver to the
              Corporation an agreement substantially in the form of Schedule "A"
              to the Shareholders Agreement agreeing to be bound thereby as if
              he or she were an original signatory thereto and, if requested by
              the Company, any of the CAI Entities, 597858 B.C. Ltd., or Orbital
              Sciences Corporation or, if applicable, Holdings (as defined in
              the Shareholders Agreement), the Grantee must also sign and
              deliver to the Corporation the Shareholders Agreement in
              counterpart.

       (d)    Non-Transferability of Options. Except as the Board may otherwise
              determine, no Option may be transferred other than by will or by
              the laws of descent and distribution, and during a Grantee's
              lifetime an Option may be exercised only by the Grantee.

11.    FORFEITURE CONDITIONS

The Board may provide in an Award Agreement for conditions of forfeiture for
"cause" of any Grantee's rights with respect to a Grant. "Cause" shall include
engaging in an activity that is detrimental to the Company including, without
limitation, criminal activity, failure to carry out the duties assigned to the
Grantee as a result of incompetence or wilful neglect, conduct casting such
discredit on the Company as in the opinion of the Board justifies termination or
forfeiture of the Grant, or such other reasons, including the existence of a
conflict of interest, as the Board may determine. "Cause" is not limited to
events that have occurred prior to the Grantee's termination of service, nor is
it necessary that the Board's finding of "cause" occur prior to such
termination. If the Board determines, subsequent to a Grantee's termination of
service but prior to the exercise of any rights under a Grant, that either prior
or subsequent to the Grantee's termination the Grantee engaged in conduct that
would constitute "cause", then the rights with respect to a Grant shall be
forfeited.

12.    COMPLIANCE WITH SECURITIES LAWS

       (a)    The delivery of Shares upon the exercise of an Option shall be
              subject to compliance with (i) applicable federal, provincial and
              state laws and regulations, including Securities Laws, (ii) all
              applicable listing requirements of any national securities or
              stock exchange or national market system on which the Shares are
              then listed or quoted, and (iii) Company counsel's approval of all
              other legal matters in connection with the issuance and delivery
              of such Shares. The Company may also require, as a condition to
              exercise of the Option, that the Grantee make such representations
              or agreements as the Company may consider appropriate to ensure
              compliance with applicable Securities Laws.


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       (b)    All share certificates evidencing Shares issued pursuant to
              exercised Options shall bear an appropriate legend restricting
              transfer.

       (c)    It is the intent of the Company that Grants pursuant to the Plan
              and the exercise of Options granted hereunder will be made
              pursuant to exemptions from applicable Securities Laws and stock
              exchange rules. To the extent that any provision of the Plan or
              action by the Board or any Option does not comply with the
              requirements of applicable Securities Laws and/or stock exchange
              rules, it shall be deemed inoperative to the extent permitted by
              law and deemed advisable by the Board, and shall not affect the
              validity of the Plan, and the Board may make any amendments
              necessary to the Plan or any Option for such purposes.

13.    MERGERS, ETC.

Except as otherwise provided herein, all Options outstanding under the Plan
shall accelerate and become immediately exercisable for a period of not less
than fifteen days (or such longer period as the Board may prescribe) immediately
prior to the scheduled consummation of a Terminating Transaction, which exercise
shall be (i) conditioned upon the consummation of the Terminating Transaction
and (ii) effective only immediately before the consummation of such Terminating
Transaction. Upon consummation of any such event, the Plan and all outstanding
but unexercised Options shall terminate. Notwithstanding the foregoing, to the
extent provision is made in writing in connection with such Terminating
Transaction for the continuation of the Plan and the assumption of Options under
the Plan theretofore granted, or for the substitution for such Options of new
Options covering the shares of a successor company, or a parent or subsidiary
thereof, with appropriate adjustments as to the number and kinds of shares or
units and exercise prices, then the Plan and Options theretofore granted shall
continue in the manner and under the terms so provided, and the acceleration and
termination provisions set forth in the first two sentences of this Section 13
shall be of no effect. The Company shall send written notice of a Terminating
Transaction to all individuals who hold Options not later than fifteen days
prior to the consummation of the Terminating Transaction.

14.    REPURCHASE OF SHARES AND OPTIONS

       (a)    At any time and from time to time prior to the listing of the
              Shares on a national securities or stock exchange or a national
              market system, the Company (or its designee) shall have, and a
              Grantee hereby grants to the Company (or its designee), an
              irrevocable right and option to purchase from a Grantee (or the
              Grantee's legal representative) all or any portion of the Options
              of the Grantee and any Shares acquired by the Grantee pursuant to
              the exercise of Options under this Plan. The Company may exercise
              such right and option by delivering to the Grantee a notice
              specifying the number of Shares and/or Options to be purchased and
              the Fair Market Value of a Share. The Company may assign its right
              and option to purchase a Grantee's Shares and/or Options.

       (b)    The price payable by the Company for Shares acquired pursuant to
              this Section 14 shall be the Fair Market Value of the Shares and
              the price payable by the Company for Options acquired pursuant to
              this Section 14 shall be the amount, if


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              any, by which the Fair Market Value of a Share exceeds the
              exercise price per Share of such Option multiplied by number of
              Shares issuable upon exercise.

15.    TAXES

The Board shall make such provisions and take such steps as it deems necessary
or appropriate for the withholding of any federal, provincial, state, local and
other tax required by law to be withheld by the Company with respect to the
grant or exercise of Options, or with respect to the disposition of Shares
acquired pursuant to the Plan, including, but without limitation, the deduction
of the amount of any such withholding tax from any compensation or other amounts
payable to a Grantee, or requiring a Grantee (or the Grantee's beneficiary or
legal representative), as a condition of a Grant or exercise of an Option, to
pay to the appropriate Participating Company any amount required to be withheld,
or to execute such other documents as the Board deems necessary or desirable in
connection with the satisfaction of any applicable withholding obligation.

16.    EMPLOYMENT RIGHTS

Neither the adoption of the Plan nor the making of any Grants shall confer upon
any Grantee any right to continue as an Employee, officer or director of any
Participating Company or affect in any way the right of any Participating
Company to terminate the Employee, officer or director at any time. Except as
otherwise specifically provided by the Board in any particular case, the loss of
existing or potential profit in Grants under this Plan shall not constitute an
element of damages in the event of termination of the relationship of a Grantee
even if the termination is in violation of an obligation of the Company to the
Grantee by contract or otherwise.

17.    CORPORATE ACTION

Nothing contained in the Plan or in an Award Agreement shall be construed so as
to prevent any Participating Company from taking corporate action which is
deemed by the Company or the Participating Company, acting in good faith, to be
appropriate or in its best interest, whether or not such action would have an
adverse effect on the Plan or any outstanding Grant, provided that the Company
shall not undertake any such corporate action with the intent to adversely
prejudice any outstanding Grant.

18.    AMENDMENT OR TERMINATION OF PLAN

       (a)    Neither the adoption of the Plan nor the making of any Grants
              shall affect the Company's right to grant Options outside of the
              Plan to any Person that is not subject to the Plan, to issue to
              such Persons Shares as a bonus or otherwise, or to adopt other
              plans or arrangements under which Shares may be issued.

       (b)    The Board may at any time discontinue Grants under the Plan. With
              the consent of the Grantee, the Board may at any time cancel an
              existing Grant in whole or in


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              part and make any other Grant for such number of Shares as the
              Board specifies. The Board may at any time, prospectively or
              retroactively, amend the Plan or any outstanding Grant for the
              purpose of satisfying any changes in applicable tax laws or
              regulations or for any other purpose that may at the time be
              permitted by law, or may at any time terminate the Plan as to
              further Grants, but no such amendment shall materially adversely
              affect the rights of any Grantee (without the Grantee's consent)
              under any outstanding Grant. In addition, the Board may at any
              time, prospectively or retroactively, amend the Plan without the
              consent of the Grantees for the purpose of complying with the
              requirements of any national securities or stock exchange on which
              the Shares are to be listed.

19.    GENERAL PROVISIONS

       (a)    Titles and Headings. Titles and headings of sections of the Plan
              are for convenience of reference only and shall not affect the
              construction of any provision of the Plan.

       (b)    Governing Law. The Plan shall be governed by, interpreted under
              and construed and enforced in accordance with the internal laws,
              and not the laws pertaining to conflicts or choice of laws, of the
              Province of British Columbia and the federal laws of Canada
              applicable therein.

       (c)    Severability. If any provision of the Plan or any Award Agreement
              shall be determined to be illegal or unenforceable by any court of
              law in any jurisdiction, the remaining provisions hereof and
              thereof shall be severable and enforceable in accordance with
              their terms, and all provisions shall remain enforceable in any
              other jurisdiction.

The Plan was duly adopted by the board of directors of the Company as of
December 22, 1999.


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                                                  Susan Herlick
                                          Assistant Secretary of the Company


The Plan was duly approved by the shareholders of the Company on December 22,
1999.

                                      ----------------------------------------
                                                  Susan Herlick
                                          Assistant Secretary of the Company