<PAGE>

                                                                    EXHIBIT 10.6

                   FOURTH AMENDMENT TO CODE SHARE AND REVENUE
                          SHARING AGREEMENT AND RELEASE

         THIS FOURTH AMENDMENT TO CODE SHARE AND REVENUE SHARING AGREEMENT AND
RELEASE (this "Fourth Amendment") is made and entered as of September 5, 2003
(the "Effective Date"), between AMERICA WEST AIRLINES, INC., a Delaware
corporation ("AWA"), MESA AIRLINES, INC., a Nevada corporation ("Mesa"), AIR
MIDWEST, INC., a Kansas corporation ("AM"), and FREEDOM AIRLINES, INC., a Nevada
corporation ("Freedom").

         RECITALS:

         A.       AWA, Mesa, AM and Freedom are parties to that certain Code
Share and Revenue Sharing Agreement, dated to be effective February 1, 2001, as
amended by that certain First Amendment to Code Share and Revenue Sharing
Agreement, dated to be effective April 27, 2001, that certain Second Amendment
to Code Share and Revenue Sharing Agreement, dated to be effective October 24,
2003, and that certain Third Amendment to Code Share and Revenue Sharing
Agreement, dated to be effective January 29, 2003 (the "Code Share Agreement").
All capitalized terms used herein, but not otherwise defined herein, shall have
the meaning given to such terms in the Code Share Agreement.

         B.       The Code Share Agreement requires Mesa to provide certain
Flight Services and Other Services for AWA, pursuant to the terms and conditions
of the Code Share Agreement.

         C.       AWA and Mesa desire to amend the Code Share Agreement pursuant
to the terms and conditions of this Fourth Amendment.

         D.       AWA and Mesa, subject to certain exceptions, desire to release
the other from certain amounts owed under the Code Share and Revenue Sharing
Agreement dated July 15, 1998, as amended ("Original Agreement") and the Code
Share Agreement.

         E.       In connection with the execution of this Amendment, AWA
intends to compensate Mesa in an amount equal to $[. . . *** . . .] ("Payment
Amount"), which amount shall be offset and paid pursuant to the terms of this
Fourth Amendment.

         NOW, THEREFORE, in consideration of the promises, covenants,
representations and warranties hereinafter set forth, and for other valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, AWA
and Mesa, and Freedom and AM as Affiliated Service Providers under and pursuant
to the Code Share Agreement, agree as set forth below.


<PAGE>

         AMENDMENTS:

         1.       The Parties agree that the first paragraph of Section 2.1 of
                  the Code Share Agreement is amended in its entirety as
                  follows:

                  Flight Service. During the term of this Agreement, Mesa (and
                  its Affiliated Service Providers) shall operate America West
                  Express air transportation services (the "Flight Services"),
                  using the Fleet of Aircraft established pursuant to Section
                  2.2, to and from the cities and based upon the schedule
                  established from time to time by AWA (the "Schedule") in
                  written notice to Mesa (a "Schedule Notice"). For purposes of
                  this Agreement, "Flights" means flights operated pursuant to
                  the Schedule. AWA may change the Schedule by issuance of a
                  Schedule Notice at any time. When creating a Schedule, AWA
                  shall: (i) take into account Mesa's (or its Affiliated Service
                  Providers') aircraft maintenance requirements; (ii) create a
                  Schedule which will permit Mesa (or its Affiliated Service
                  Providers)to schedule flight crews in a manner consistent with
                  industry operational practices; (iii) schedule block times
                  based on AWA's internal block time policy; (iv) provide for
                  the following turn times: (a) in a hub location: 20 minutes
                  for Dash 8s and 25 minutes for any Aircraft in the CRJ
                  Subfleet; and (b) in other stations: 15 minutes for Dash 8s
                  and 20 minutes for any Aircraft in the CRJ Subfleet; (v) take
                  into account airport facilities available for Aircraft
                  handling; (vi) provide for maintenance as required by Section
                  2.6.3 and scheduled heavy maintenance on Aircraft as required
                  from time to time; and (vii) provide for at least 45 days
                  prior notice of any holiday cancellations. Mesa (and its
                  Affiliated Service Providers) shall implement all changes in
                  the Schedule contained in a Schedule Notice in accordance with
                  AWA's scheduling requirements within 60 days after Mesa's
                  receipt of a Schedule Notice. Mesa or any of its affiliates
                  shall not provide any flight service for any other airline for
                  flights that originate in or end in Phoenix, Arizona, other
                  than flights approved in advance by AWA, in writing, that are
                  scheduled or operated for maintenance requirements only;
                  provided, however, that Mesa, until 11:59 p.m. Phoenix time on
                  March 1, 2004, may operate [. . . *** . . .] as United Express
                  into Phoenix, Arizona [. . . *** . . .].

         2.       The Parties agree that the introductory paragraph of Section
                  2.2.2 and Section 2.2.2(a) of the Code Share Agreement are
                  amended in their entirety as follows:

                  CRJ Fleet Expansion. Pursuant to the Aircraft Contract, Mesa
                  (or its Affiliated Service Providers) has the right to acquire
                  additional CRJ Model 900 Aircraft, by virtue of firm orders
                  (the "Firm Aircraft"), and additional CRJ Models 700 and 900
                  Aircraft, by virtue of options (the "Option Aircraft"), in the
                  number and in the months set forth on Exhibit A, attached
                  hereto. The Firm Aircraft consist of CRJ Model 900 Aircraft
                  and the Option Aircraft consist of CRJ Models 700 and 900
                  Aircraft as set forth in Exhibit A. For purposes of this
                  Agreement, the CRJ

<PAGE>

                  Model 200s shall be a "CRJ Subfleet" and the CRJ Model 700s
                  and 900s shall be a "CRJ Subfleet". The term "CRJ" is intended
                  to refer to CRJ Models 200s, 700s or 900s, as applicable.

                  (a)      Each of the Firm Aircraft shall be placed into Flight
                           Services by Mesa (or its Affiliated Service
                           Providers) in the calendar months set forth on
                           Exhibit A (the "Delivery Schedule"). Mesa shall
                           provide AWA with at least 90 days' prior written
                           notice of the week each of the Firm Aircraft will be
                           placed into Flight Service under this Agreement and
                           at least 60 days' prior written notice of the date on
                           which each of the Firm Aircraft will be placed into
                           Flight Service under this Agreement (each, a
                           "Scheduled Delivery Date").

         3.       The Parties agree that Section 2.2.2(c) of the Code Share
                  Agreement is amended by: (A) adding the phrase: (i) "or in the
                  calendar month in which the Firm Aircraft is to be delivered
                  pursuant to the Delivery Schedule, as applicable" after
                  "Scheduled Delivery Date" in the first sentence of Section
                  2.2.2(c); and (ii) "or the calendar month in which the Firm
                  Aircraft is to be delivered pursuant to the Delivery Schedule,
                  as applicable" after the term "Scheduled Delivery Date" is
                  used in the second and third sentences of Section 2.2.2(c);
                  and (B) adding the parenthetical "(as initially established by
                  the Delivery Notice, as defined in Section 2.2.2(e))" after
                  the term "Scheduled Delivery Date" in the Section.

         4.       The Parties agree that the Code Share Agreement is amended by
                  adding the following as Section 2.2.2(d): Notwithstanding
                  anything contained in Sections 2.2.2(a) and (c) to the
                  contrary, Mesa, by providing AWA with written notice (a "Delay
                  Notice") at least [. . . *** . . .] prior to the first day of
                  the calendar month in which a Firm Aircraft is to be delivered
                  pursuant to the Delivery Schedule (the "Scheduled Delivery
                  Month"), may, at its sole option and without penalty of any
                  kind, delay the Scheduled Delivery Month for a Firm Aircraft
                  by up to [. . . *** . . .] if either: (i) Bombardier notifies
                  Mesa, in writing, that Bombardier will be unable to deliver
                  the applicable Firm Aircraft on time; or (ii) if Mesa, despite
                  using commercially reasonable efforts, is unable to obtain
                  financing for the applicable Firm Aircraft, timely to deliver
                  the Firm Aircraft in the Scheduled Delivery Month. The Delay
                  Notice shall: (i) be accompanied with the Bombardier notice or
                  a reasonable description of the efforts made by Mesa to obtain
                  the financing and the reason for not obtaining the financing,
                  as applicable; and (ii) establish the new Scheduled Delivery
                  Month in which the Firm Aircraft being delayed is to be
                  delivered. Mesa shall only be entitled to extend the Scheduled
                  Delivery Month for a Firm Aircraft one time pursuant to this
                  Section 2.2.2(d).

<PAGE>

         5.       The Parties agree that the Code Share Agreement is amended by
                  adding the following as Section 2.2.2(e):

                  Bombardier Delivery Date. Pursuant to Mesa's agreement with
                  Bombardier, Bombardier is required to provide Mesa with 90
                  days' written notice of the scheduled delivery week of each
                  Firm Aircraft (the "B-90 Notice"). Based on the B-90 Notice,
                  Mesa, at least 60 days prior to the Scheduled Delivery Date,
                  provides AWA with written notice of the Scheduled Delivery
                  Date pursuant to the last sentence of Section 2.2.2(a) (the
                  "Delivery Notice") for each Firm Aircraft. For purposes of
                  this Section 2.2.2(e), Mesa, based upon a change in delivery
                  dates received by Mesa from Bombardier, shall have the right
                  to extend the Scheduled Delivery Date to a new date certain
                  once for each Firm Aircraft by providing AWA with written
                  notice at least 45 days prior to the Scheduled Delivery Date
                  established by the applicable Delivery Notice (the "Extension
                  Notice"). If a Firm Aircraft is delivered by Mesa to AWA and
                  is ready to be placed into Flight Services prior to the
                  Scheduled Delivery Date established by the Delivery Notice (as
                  may be extended by an Extension Notice), then AWA shall not be
                  obligated to make any payment under this Agreement for such
                  Firm Aircraft until the Scheduled Delivery Date established by
                  Mesa pursuant to the Delivery Notice (as may be extended by an
                  Extension Notice). If a Firm Aircraft is delivered by Mesa to
                  AWA and is ready to be placed into Flight Services after the
                  Scheduled Delivery Date established by the Delivery Notice (as
                  may be extended as a result of an Excusable Delay or an
                  Extension Notice), then, notwithstanding anything in Section
                  2.2.2(c) to the contrary, Mesa, within 30 days after receipt
                  of written demand from AWA, shall pay to AWA an amount equal
                  to $[. . . *** . . .] for each day following the fifth day
                  after the Scheduled Delivery Date that the Firm Aircraft is
                  not delivered until the date that the Firm Aircraft is
                  available to AWA to be placed into Flight Services under this
                  Agreement ("Delay Amount"), not to exceed for any Firm
                  Aircraft the greater of (i) $[. . . *** . . .] or (ii) the
                  amount paid by Bombardier to Mesa as damages for the late
                  delivery of such Firm Aircraft. An "Excusable Delay" shall be
                  defined to include delays commencing after the date of the
                  Delivery Notice and before the Scheduled Delivery Date (as may
                  be extended by an Extension Notice) and occasioned by the
                  following causes:

                             i.     acts of God;

                            ii.     war, warlike operations, act of the enemy,
                                    armed aggression, civil commotion,
                                    insurrection, riot or embargo;

                           iii.     fire, explosion, earthquake, lightning,
                                    flood, drought, windstorm or other action of
                                    the elements or other catastrophic or
                                    serious accidents;

                            iv.     epidemic or quarantine restrictions;

                             v.     any change in legislation, acts, orders,
                                    directives or regulations of any
                                    governmental or other duly constituted
                                    authority (other than CRJ

<PAGE>

                                    Regulatory Changes and CRJ Airworthiness
                                    Directives) once the applicable Aircraft
                                    type has been certified by the FAA; or

                           vi.      strikes, lock-out, walk-out, and/or other
                                    labor troubles, in each case, with respect
                                    to employees of Bombardier causing cessation
                                    of work;.

                  If an Excusable Delay occurs, then the Scheduled Delivery Date
                  for purposes of this Section 2.2.2(e) shall be extended for
                  the number of days of Excusable Delay ("Excusable Delay
                  Period"), and the Delay Amount shall not begin to accrue until
                  the fifth day after the Scheduled Delivery Date, as extended
                  by the Excusable Delay Period. The terms of this Section
                  2.2.2(e) are in addition to, and not in lieu of, the terms of
                  Sections 2.2.2(c) and 2.2.2(d).

         6.       The Parties agree that the Code Share Agreement is amended by
                  adding the following as Section 2.2.2(f):

                  [. . . *** . . .]

         7.       The Parties agree that the Code Share Agreement is amended by
                  adding the following as Section 2.2.2(g):

                  [. . . *** . . .]

         8.       The Parties agree that Section 2.2.3 of the Code Share
                  Agreement is amended by adding the following:

                  Elimination of CRJ Model 700s. In addition to the terms of
                  Sections 2.2.4 and 2.2.5(d), (i) in recognition of the total
                  of four (4) CRJ Model 900s to be delivered pursuant to the
                  Delivery Schedule in October 2003, November 2003 and December
                  2003, Mesa shall remove, or cause Freedom to remove, from the
                  CRJ Subfleet one (1) CRJ Model 700 at 11:59 p.m. Phoenix time
                  on each of the following dates: November 24, 2003; December 1,
                  2003; December 2, 2003; and December 24, 2003; and (ii) on
                  each date that a CRJ Model 900 is placed into Flight Services
                  pursuant to the terms of this Agreement, commencing with the
                  CRJ Model 900 to be delivered in January 2004, Mesa shall
                  remove, or shall cause Freedom to remove, from the CRJ
                  Subfleet a CRJ Model 700 for each CRJ Model 900 placed into
                  Flight Services, until the number of CRJ Model 700s in the CRJ
                  Subfleet is reduced to zero, which, pursuant to the Delivery
                  Schedule, is scheduled to occur upon the delivery of the March
                  2004 CRJ Model 900. AWA shall reimburse Mesa for the actual,
                  out-of-pocket costs or expenses incurred by Mesa (or Freedom
                  as applicable) as a direct result of the painting (including
                  the days out of service for painting) of each CRJ Model 700
                  removed pursuant to this Section 2.2.3 within thirty (30) days
                  after receipt of an invoice from Mesa together with
                  commercially reasonable evidence of such costs or expenses.

<PAGE>

         9.       The Parties agree that Section 2.2.4 of the Code Share
                  Agreement is amended in its entirety as follows:

                  Additional CRJ Fleet Reduction. In addition to the terms of
                  Sections 2.2.3 and 2.2.5, upon 180 days' prior written notice
                  from AWA to Mesa given from time to time during the Term, AWA,
                  subject to limitations set forth in the next sentence, may
                  require Mesa to reduce, or require Mesa to cause Freedom to
                  reduce, the number of Aircraft in the combined CRJ Subfleets.
                  AWA shall not require Mesa to reduce, or require Mesa to cause
                  Freedom to reduce, the number of Aircraft: (i) in the CRJ
                  Model 200 CRJ Subfleet prior to January 1, 2007; (ii) in the
                  CRJ Model 900s (and CRJ Model 700s if any CRJ Model 900s are
                  replaced pursuant to Section 2.2.2(g)) CRJ Subfleet prior to:
                  (1) January 1, 2007, if Mesa does not induct any of the Put
                  CRJ 900s pursuant to Section 2.2.2(f) (as may be replaced
                  pursuant to Section 2.2.2(g) with CRJ Model 700s), or (2) July
                  1, 2006, if Mesa inducts one or more of the Put CRJ 900s
                  pursuant to Section 2.2.2(f) (as may be replaced pursuant to
                  Section 2.2.2(g) with CRJ Model 700s); and (iii) in the
                  combined CRJ Subfleets by more than one Aircraft in any Six
                  Calendar Month Period; notwithstanding such limitation, during
                  the two (2) Six Calendar Month Periods commencing January 1,
                  2007 and July 1, 2007, AWA may reduce the combined CRJ
                  Subfleets by either: (i) up to two (2) CRJ Model 200 Aircraft;
                  or (ii) one (1) CRJ Model 900 or CRJ Model 700 Aircraft and
                  one (1) CRJ Model 200 Aircraft, in each such Six Calendar
                  Month Periods. For purposes of this Agreement, "Six Calendar
                  Month Period" means each period during the Term (as defined
                  below) commencing on January 1 and ending on June 30 and
                  commencing on July 1 and ending on December 31.

         10.      The Parties agree that Section 2.2.5 of the Code Share
                  Agreement is amended in its entirety as follows:

                  Additional Aircraft Reduction.

                  (a)      Effective July 1, 2003, the Subfleet of Beech 1900s
                           was reduced to zero. From and after July 1, 2003,
                           Mesa shall no longer provide any Flight Services
                           using Beech 1900s and AWA shall have no payment or
                           other obligations under this Agreement accruing or
                           arising after July 1, 2003 in regards to any Beech
                           1900s. All references to the Beech 1900s and the
                           subcontracting of services relating to the Beech
                           1900s shall be eliminated from the Agreement
                           effective as of July 1, 2003.

                  (b)      Mesa, on July 1, 2003, removed one (1) Dash 8
                           Aircraft from the Dash 8 Subfleet and on September 3,
                           2003, will remove two (2) Dash 8 Aircraft from the
                           Dash 8 Subfleet. At any time during the Term after
                           August 25, 2007,

<PAGE>

                           AWA may require Mesa to reduce the Subfleet of Dash
                           8s to zero by providing Mesa with at least 180 days'
                           prior written notice of AWA's election to eliminate
                           the Dash 8s on or after such date (the "Dash 8
                           Elimination Notice"). The Dash 8 Elimination Notice
                           may be given at any time during the Term on or after
                           February 27, 2007.

                  (c)      Mesa removed one (1) CRJ Model 200 from the CRJ
                           Subfleet (for a total of five (5) CRJ Model 200s) on
                           each of the following dates:

                           April 27, 2003
                           June 4, 2003
                           June 22, 2003
                           June 27, 2003
                           July 2, 2003

                           reducing the CRJ Model 200 CRJ Subfleet to 18
                           Aircraft.

                  (d)      Mesa removed two (2) CRJ Model 700s from the CRJ
                           Subfleet at 11:59 p.m. Phoenix time on September 2,
                           2003. Mesa shall remove, or cause Freedom to remove,
                           (or not place into Flight Services, as applicable)
                           one (1) CRJ Model 700 at 11:59 p.m. Phoenix time on
                           September 14, 2003, and two (2) CRJ Model 700s at
                           11:59 p.m. Phoenix time on September 21, 2003 from
                           the CRJ Subfleet, reducing the CRJ Model 700s in the
                           applicable CRJ Subfleet to 10.

                  (e)      On or before October 31, 2003, AWA, by written notice
                           to Mesa, shall have the right to cause the 12 CRJ
                           Model 900s scheduled to be delivered into Flight
                           Services from April, 2005 to November, 2005 (the
                           "Rejectable CRJs"), pursuant to the Delivery
                           Schedule, not to be added to the CRJ Subfleet and not
                           to be placed into Flight Services (the "900 Election
                           Notice"). If AWA does not issue the 900 Election
                           Notice, timely, and such failure to issue the 900
                           Election Notice, timely, continues for 15 days after
                           AWA's receipt of written notice from Mesa stating
                           that AWA failed to issue the 900 Election Notice,
                           then AWA shall have no further right to issue a 900
                           Election Notice and reject the Rejectable CRJs. If
                           AWA issues the Election Notice as provided by this
                           Section 2.2.5(e), then none of the Rejectable CRJs
                           shall be added to the CRJ Subfleet or placed into
                           Flight Services under this Agreement.

                  (f)      Neither Mesa, AM nor Freedom shall operate any
                           Aircraft removed from Flight Services for itself or
                           any other airline while the Aircraft are marked with
                           AWA's livery

<PAGE>

                  (g)      From and after the date each Aircraft was or is
                           removed from Flight Services pursuant to any section
                           of this Agreement, AWA had and shall have no further
                           payment or other obligation under this Agreement for
                           such Aircraft.

         11.      The Parties agree that Section 2.2.6 is amended in its
                  entirety as follows:

                  Spares. Mesa shall have available 1 spare CRJ Model 200, 700
                  or 900 Aircraft for Flight Services under this Agreement at
                  any time there are 25 or more Aircraft in the combined CRJ
                  Subfleets in Flight Services under this Agreement and 2 spare
                  CRJ Model 200, 700 or 900 Aircraft available for Flight
                  Services under this Agreement at any time there are 65 or more
                  Aircraft in the combined CRJ Subfleets in Flight Services
                  under this Agreement. AWA shall pay the Actual Costs,
                  Guaranteed Non-Maintenance Costs (other than overhead) and
                  Guaranteed Maintenance Costs actually incurred by or payable
                  to Mesa for each spare Aircraft as provided in Section 7.

         12.      The Parties agree that the Code Share Agreement is amended by
                  adding the following as Section 2.2.8:

                  Affiliated Service Provider Aircraft. Mesa, with at least 30
                  days' prior written notice to AWA, may substitute any Aircraft
                  operated by Mesa or Freedom under or pursuant to this
                  Agreement with an aircraft of the same model, capacity,
                  configuration and meeting the other requirements of this
                  Agreement, operated by an Affiliated Service Provider (each, a
                  "Substituted Aircraft"); provided that Mesa and such
                  Affiliated Service Provider have complied with the provisions
                  of Section 2.1 and all other provisions relating to Affiliated
                  Service Providers. Upon each substitution, each Substituted
                  Aircraft shall become an Aircraft for all purposes of this
                  Agreement. Mesa shall reimburse AWA for any out-of-pocket
                  costs or expenses incurred by AWA as a result of the
                  substitution of Aircraft under this Section 2.2.8 within
                  thirty (30) days after receipt of an invoice from AWA together
                  with commercially reasonable evidence of the out-of-pocket
                  costs or expenses actually incurred by AWA.

         13.      The Parties agree that the Code Share Agreement is amended by
                  deleting Section 7.1.8.

         14.      The parties agree that the Code Share Agreement is amended by
                  adding the following as a new Section 7.10:

                  Station Costs. AWA shall reimburse to Mesa the costs and
                  expenses incurred by Mesa at stations maintained by Mesa in
                  the amounts and at the rates set forth in Exhibit B, attached
                  hereto (the "Station Costs"). Mesa shall invoice, as part of
                  the "Estimated Costs", and AWA shall pay the Station Costs on
                  a monthly basis

<PAGE>

                  in accordance with Section 7.5.1 of this Agreement. Pursuant
                  to Section 7.5.2 of this Agreement, Mesa shall include in each
                  Incurred Costs Statement the final amount of the Station Costs
                  payable by AWA to Mesa for each applicable calendar month, all
                  as calculated in accordance with Exhibit B, attached hereto.
                  Underpayments and overpayments of Station Costs shall be
                  reconciled in the manner set forth in Section 7.5.2 for
                  "Incurred Costs". The terms of Section 7.5.4 shall be
                  applicable to the Station Costs included or not included in
                  each applicable Incurred Costs Statement; provided, however,
                  that if any landlord or operator of any station is entitled to
                  retroactively adjust station rents, then the applicable
                  station rent shall be adjusted by Mesa as soon as reasonably
                  practicable after such adjustment and shall be paid by or
                  reimbursed to AWA within 30 days after Mesa provides AWA with
                  notice of such adjustment and recalculation. All of the terms
                  contained in Sections 7.8 and 7.9 shall apply to the
                  invoicing, paying, collecting and auditing of Station Costs.

                  AWA and Mesa intend for the Station Costs to be effective
                  retroactive to January 1, 2003. As soon as practicable and in
                  no event later than 90 days after the Effective Date of the
                  Fourth Amendment, Mesa shall submit to AWA a reconciliation of
                  the Station Costs (the "Reconciliation") since January 1, 2003
                  calculated in accordance with Exhibit F. To the extent the
                  Reconciliation discloses that sums are due from AWA to Mesa,
                  AWA shall pay such sums to Mesa.

         15.      The Parties agree that Section 8.1 of the Code Share Agreement
                  is amended as follows:

                  Term. The term of this Agreement (the "Term") commences on the
                  Effective Date retroactive to the Contract Date (the
                  "Commencement Date") and shall expire at 11:59 p.m., Phoenix
                  time, on June 30, 2012 ("Expiration Date"), unless earlier
                  terminated as provided in this Agreement. Notwithstanding the
                  foregoing to the contrary, if the 900 Election Notice is not
                  issued by AWA to Mesa as required by Section 2.2.5(e) and the
                  Rejectable CRJs are added to the CRJ Subfleet, then the
                  Expiration Date shall be extended to 11:59 p.m., Phoenix time,
                  on November 30, 2013. AWA, by written notice to Mesa at least
                  180 days prior to the Expiration Date, may extend the
                  Expiration Date for two years, expiring at 11:59 p.m., Phoenix
                  time, on June 30, 2014 or November 30, 2015, as applicable.

         16.      The Parties agree that Exhibit A to the Code Share Agreement
                  is amended in its entirety as set forth in Attachment 1 to
                  this Fourth Amendment, and Exhibit B to the Code Share
                  Agreement is amended in its entirety as set forth in
                  Attachment 2 to this Fourth Amendment.

<PAGE>

         17.      Reserved.

                  AGREEMENTS:

         18.      Release.

                  (a)      Except as provided in Section 17(c), below, AWA fully
                           and finally releases, acquits and forever discharges
                           Mesa and its parent companies and subsidiaries from
                           any and all claims or demands for any amounts owed,
                           accrued, payable, incurred, billed or invoiced
                           pursuant to the Code Share Agreement or the Original
                           Agreement for matters, services, actions, events,
                           activities or other items provided or occurring on or
                           before, or related to the period expiring on,
                           December 31, 2002.

                  (b)      Except as provided in Section 17(c), below, Mesa, AM
                           and Freedom fully and finally release, acquit and
                           forever discharge AWA and its parent companies and
                           subsidiaries from any and all claims or demands for
                           any amounts owed, accrued, payable, incurred, billed
                           or invoiced pursuant to the Code Share Agreement or
                           the Original Agreement for matters, services,
                           actions, events, activities or other items provided
                           or occurring on or before, or related to the period
                           expiring on, December 31, 2002.

                  (c)      Notwithstanding the foregoing, the parties agree that
                           the releases set forth in subsections (a) and (b)
                           above shall not apply to (i) any amounts accruing or
                           payable under the Code Share Agreement after December
                           31, 2002 for services, actions, events, activities or
                           other items occurring after December 31, 2002; (ii)
                           any amounts owed by Mesa pursuant to Section 5 of the
                           Code Share Agreement (provided, however, that AWA
                           shall not use its right of offset for these amounts
                           until payment by AWA of any amounts owing pursuant to
                           the Reconciliation, unless Mesa has not provided AWA
                           with the Reconciliation pursuant to Section 7.10
                           within 90 days of the Effective Date of this Fourth
                           Amendment in which case AWA may exercise its offset
                           rights for these amounts at any time after the 90th
                           day after the Effective Date of this Fourth
                           Amendment); (iii) any Transition Reimbursement owed
                           by AWA pursuant to Section 2.2.7 of the Code Share
                           Agreement; (iv) any amounts to be paid by AWA
                           pursuant to paragraph 18 below; (v) any amount
                           payable by AWA to Mesa for the closure of the
                           maintenance base in Columbus, Ohio pursuant to
                           Section 2.6.3 of the Code Share Agreement; (vi) any
                           amounts owed by Mesa to AWA as reimbursement for
                           overpayment of landing fees by AWA to Mesa; or (vii)
                           any amounts payable by Mesa to AWA as reimbursement
                           for Aviation Security Infrastructure Fees.

<PAGE>

                  Payment Obligation. On the Effective Date, AWA shall be
                  obligated to pay to Mesa the Payment Amount, [. . . *** . . .]

         19.      Withdrawal of Notice. AWA withdraws all notices that it
                  provided to Mesa for the cancellation of three (3) CRJ Model
                  700s and agrees and acknowledges that, as of the Effective
                  Date of this Fourth Amendment, the number of CRJ Model 700s in
                  the CRJ Subfleet (and committed to be added to the CRJ
                  Subfleet) is, in the aggregate, fifteen (15).

         20.      CRJ Model 200s. As of the Effective Date of this Fourth
                  Amendment, the number of CRJ Model 200s in the CRJ Subfleet is
                  eighteen (18).

         21.      Effect. Except as set forth in this Fourth Amendment, all of
                  the terms and conditions of the Code Share Agreement remain in
                  full force and effect.

         22.      Counterparts. This Fourth Amendment may be executed in
                  counterparts, all of which when taken together shall be one
                  and the same document.

         23.      Entire Agreement. This Fourth Amendment constitutes the entire
                  agreement between the parties with respect to the subject
                  matter hereof and supersedes all prior understandings with
                  respect thereto.

                                            AMERICA WEST AIRLINES, INC.

                                            By:    /s/ J. Scott Kirby
                                                   ----------------------------
                                            Name:  J. Scott Kirby
                                            Title: EVP - Sales and Marketing

                                            MESA AIRLINES, INC.

                                            By:    /s/ Jonathan Ornstein
                                                   -----------------------------
                                            Name:  Jonathan Ornstein
                                            Title: Chief Executive Officer

                                            AIR MIDWEST, INC.

<PAGE>

                                            By:    /s/ George Murnane
                                                   -----------------------------
                                            Name:  George Murnane
                                            Title:------------------------------

                                            FREEDOM AIRLINES, INC.

                                            By:    /s/ Michael Lotz
                                                   -----------------------------
                                            Name:  Michael Lotz
                                            Title:------------------------------

<PAGE>

                                    EXHIBIT A
                                   CRJ-700/900
                                DELIVERY SCHEDULE

<TABLE>
<CAPTION>
                         CURRENT                            NEW                                             TOTAL
                         CRJ-900          CRJ-700         CRJ-900                                         CRJ-7/900
                        DELIVERIES      REDUCTIONS       DELIVERIES        CRJ-700         CRJ-900          FLEET
                        ----------      ----------       ----------        -------         -------          -----
<S>                   <C>             <C>               <C>             <C>             <C>              <C>
9/2/03                [... *** ...]   [... *** ...]     [... *** ...]   [... *** ...]   [... *** ...]    [... *** ...]
Sep-03
Oct-03
Nov-03
Dec-03

Jan-04
Feb-04
Mar-04
Apr-04
May-04
Jun-04
Jul-04
Aug-04
Sep-04
Oct-04
Nov-04
Dec-04

Jan-05
Feb-05
Mar-05
Apr-05
May-05
Jun-05
Jul-05
Aug-05
Sep-05
Oct-05
Nov-05

Incremental Aircraft                  [... *** ...]     [... *** ...]
                                      -------------     -------------
</TABLE>

Note:

[... *** ...]

<PAGE>

                                    EXHIBIT A
                               OPTION CRJ-700/900
                                DELIVERY SCHEDULE

<TABLE>
<CAPTION>
       DELIVERY                                            OPTION
        MONTH                                            CRJ-7/900
----------------------------------------------------------------------
<S>    <C>                                               <C>
       Jan-04                                            [... *** ...]
       Feb-04
       Mar-04
       Apr-04
       May-04
       Jun-04
       Jul-04
       Aug-04
       Sep-04
       Oct-04
       Nov-04
       Dec-04
----------------------------------------------------------------------
Each calendar month
thereafter through Oct-07                                [... *** ...]
----------------------------------------------------------------------
                                                         [... *** ...]
</TABLE>

Note:

[... *** ...]

<PAGE>

                                    EXHIBIT B

<TABLE>
<CAPTION>
                                     Cost per
                      Monthly      Departure >3      Cost/
                      Cost Per      Departures     Departure      B19, DH8 and CRJ 200 Markets Covered by Model (as
  Aircraft Type       Station        per Day        PHX Hub                           of 12/31/02)
-------------------------------------------------------------------------------------------------------------------
<S>               <C>            <C>             <C>             <C>
B19               [... *** ...]  [... *** ...]   [... *** ...]   [... *** ...]
DH8

CRJ 200

CRJ 700

CRJ 900
</TABLE>

Mexico Stations
GDL (CRJ 200)       [... *** ...]

Each month, overall station cost reimbursement (exclusive of station rent) will
be determined by the sume of:

[... *** ...]

Notes

[... *** ...]