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                                   Exhibit 99

                                   Exhibit 99

                              Internal Market Rules

         The  following  rules are to be applied to the operation of the DynCorp
Internal  Market.  DynEx  may,  from  time to  time,  change  Market  rules  and
procedures.

         It is anticipated  that the Market will permit existing and new DynCorp
stockholders  to sell Shares on four  predetermined  dates each year (the "Trade
Dates").  Such sales will be made at the  prevailing  Formula  Price to eligible
employees  and  directors  of DynCorp  and to  trustees  and  administrators  of
DynCorp's  qualified and  non-qualified  employee benefit plans. Any employee or
director who resides in a state wherein direct  individual  purchase through the
Market is permitted,  whether by reason of registration  under or exemption from
state  securities  laws,  is eligible for  purposes of the Market.  In addition,
DynCorp will be authorized, but not obligated, to sell or purchase Shares in the
Market,  provided  that DynCorp will not be both a seller and a purchaser on the
same Trade Date.

         All record  stockholders of common stock of DynCorp will be eligible to
sell some or all of the shares  owned by them on any Trade Date;  in the case of
shares owned  beneficially,  sales must be directed by the record  holder and in
accordance with any relevant  instrument  relating to the rights and obligations
of the  respective  parties.  In the event that the  aggregate  number of shares
offered for sale by the sellers is greater than the  aggregate  number of shares
sought to be purchased by authorized  buyers and DynEx on a specific Trade Date,
offers to sell will be treated in the following manner.

         (a) Offers to sell 500 Shares or less and up to the first 500 Shares if
         more than 500 Shares are  offered by any seller  will be  accepted  for
         purchase first. If, however,  there are insufficient purchase orders to
         support the primary  allocation of 500 Shares or less per seller,  then
         the purchase  orders will be allocated  on an equal  percentage  of the
         first 500 Shares per seller, among all of the proposed sellers.

         (b) If additional  purchase orders remain open after application of the
         foregoing  process,  the same  procedure  will be applied to  remaining
         offers to sell the first 10,000 Shares  remaining to be offered by each
         seller.

         (c) If additional  purchase orders remain open after application of the
         foregoing process, offers to sell more than the first 10,500 Shares per
         seller  addressed in (a) and (b) above will be accepted for purchase on
         a pro-rata basis based on the number of shares  remaining to be offered
         by all sellers.

         (d) Subject to applicable  legal or  contractual  restrictions  and the
         availability  of  funds,  DynCorp  may,  in  its  discretion,  purchase
         sufficient  Shares on each Trade Date so that each stockholder  wishing
         to sell Shares  will be able to sell  additional  Shares in  accordance
         with the above preferences.

         If the aggregate  purchase orders exceed the number of shares available
for sale, the following prospective  purchasers will have priority, in the order
listed:

         1.        the administrator of the Employee Stock Purchase Plan;
         2.        the trustees of the Savings and Retirement Plan;
         3.        eligible employees and directors, on a pro rata basis; and
         4.        the trustees of the Employee Stock Ownership Plan.

         To the  extent  that  the  aggregate  number  of  shares  sought  to be
purchased  exceeds the aggregate number of shares for sale,  DynCorp may, but is
not obligated to, sell authorized, but unissued Shares in the Market.

         Buck  Investment  Services,  an NASD-  registered  broker-dealer,  will
maintain the limited  secondary  market for  DynCorp.  Prior to each Trade Date,
Buck  Investment  Services will notify record  holders in writing of the pending
Trade Date and price at which  shares  will be sold,  and  provide  instructions
regarding   submission   of  stock   certificates   and   other   administrative
requirements.  Buck  Investment  Services  will  receive  all sell  orders  from
stockholders  of record and buy orders from  authorized  buyers and DynCorp,  if
applicable. On each Trade Date, Buck Investment Services will clear trades on an
agency only,  unsolicited basis between sellers and buyers of Shares (including,
to the extent  applicable,  DynCorp)  according to the priority rules  described
above. Buck Investment Services will then forward payments to sellers, minus the
commission,  and will issue,  in  book-entry  form unless  certificated  form is
required by law, the Shares to the buyers.  Commission  provisions are discussed
in the underlying agreement with Buck Investment Services.

         Individual  sellers  will  pay a sales  commission  to Buck  Investment
Services of 2% of the sales  price;  the Company and the Savings and  retirement
Plan will not pay such a commission. Buyers will not pay any commission.

         For  purchases by entities  such as plan  administrators,  DynCorp will
coordinate  wire  transfers  of payments to Buck  Investment  Services'  Special
Reserve  Account,  established  for  the  protection  of  customer  funds,  with
transmittal  instructions  to be issued no later than noon on the first business
day following the day Buck  Investment  Services  advises  DynCorp of the amount
required.  For purchases by individuals,  deposits in good Federal Funds must be
received by Buck Investment Services' Special Reserve Account prior to the trade
date.

         Buck  Investment  Services  will  not  buy or sell  Shares  for its own
account.

         Shares issued as a result of purchases in the Market will be subject to
the following restrictions regarding resale or other distribution of the shares:

         Shares  purchased by any  purchaser  on the Internal  Market may not be
         sold or  transferred  by the holder  thereof to any third party,  other
         than (1 by  descent  or  distribution,  (2) by bona fide  gift,  (3) by
         transfers  within  a trust,  or other  qualified  tax-free  entity,  or
         distribution by the trust or such entity to a participant,  in the case
         of an employee  benefit  plan,  or a beneficial  owner,  in the case of
         another  tax-free  entity,  or (4) by bona fide sale  after the  holder
         thereof  has first  offered  in writing to sell the share to DynCorp at
         the same price and under  substantially  the same terms as apply to the
         intended  sale and  DynCorp has failed or declined in writing to accept
         such  terms  within 14 days of  receipt  of such  written  offer by the
         Corporate  Secretary  of DynCorp or has refused to proceed to a closing
         on the  transaction  within a  reasonable  time after such  acceptance;
         provided,  however,  that the sale to the third  party  following  such
         failure,  declination,  or refusal must be made on the same terms which
         were not  previously  accepted  by the  corporation  and within 60 days
         following  such event,  or DynCorp  must again be offered  such refusal
         rights prior to a sale of such share;  provided further,  however, that
         this Section  shall not apply to (A) any  subsequent  sale  transaction
         made through the Internal Stock Market;  (B) any  transactions  made at
         any time  while the common  stock is listed  for  trading on a national
         securities exchange or on the over-the-counter  market; or (C) sales to
         the DynCorp Employee Stock Ownership Plan.

As amended April 15, 1998