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                                                                   EXHIBIT 10.23

                                                     United Contract Nbr. 155716

                                    ZK/UNITED
                            CODE SHARE AND REGULATORY
                       COOPERATION AND MARKETING AGREEMENT

This Agreement is made and entered into by and between UNITED AIR LINES, INC.,
("UA") with its principal place of business at 1200 East Algonquin Road, Elk
Grove Township, Illinois 60007 and GREAT LAKES AVIATION Ltd. ("ZK") with its
principal place of business at 1022 Airport Parkway, Cheyenne, Wyoming 82001,
each or both parties individually or collectively referred to as "Carrier" or
"Carriers" respectively.

1.     INTRODUCTION
       ZK and UA are entering into this Agreement in order to increase each
       Carrier's opportunities to offer competitive and cost effective air
       transportation services between points in the United States. Further, ZK
       and UA wish to improve the quality of the interline air transportation
       and cargo services they now offer so as to increase the use of those
       services by the traveling and shipping public. This Agreement establishes
       binding obligations between the Carriers, expresses the Carriers
       intentions, and sets forth a framework that provides the basis to
       accomplish these goals through subsequent agreements and activities.

2.     UNDERLYING OPERATIONAL CONCEPT
       The Carriers will use a phased approach to develop and implement parallel
       marketing and operational programs to create new, value added passenger
       and cargo services and cost efficiencies by taking advantage of each
       Carrier's inherent market strengths. The transition from a United Express
       arrangement to codeshare relationship will extend until ZK has procured
       and installed the necessary automation to support the operation as an
       independent business entity. This must be completed no later than June 7,
       2002 and be hosted on a system which is technically capable of all the
       required interfaces with UA's automation systems.

3.     OBJECTIVES OF THE ZK/UA RELATIONSHIP
       Through development of the operational relationship contemplated by this
       Agreement, subject to any and all necessary governmental and regulatory
       approvals, ZK and UA intend to implement Code Share operations as defined
       in Article 4A and further described in Attachment 1, Sections A and B.

       This Agreement is not intended to restrict either Carrier's rights to
       pursue, either independently or collectively, additional access between
       any points through route acquisition.

4.     PROGRAMS
       The Carriers will develop and implement specific programs to support the
       objectives defined by this Agreement. The Attachments to this Agreement
       outline specific actions and responsibilities for implementing these
       programs. Each of the programs may be

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       incorporated into an existing ZK/UA contract or a new contract, as
       appropriate. In summary, subject to any and all applicable governmental
       laws, rules and regulations, these programs are:

       A.     CODE SHARE
              The Carriers intend to develop, in a phased approach, operations
              which include using UA's two-letter airline designator code on the
              following routes, as further specified in Attachments 1 and 1A
              ("Code Share"):

                     - To and from points within the UA's system in the US.

       B.     CODE SHARE EMERGENCY PROCEDURES
              In the event of an incident involving a Code Share flight, both
              Carriers agree to implement the emergency procedures specified in
              Attachment 2.

       C.     REGULATORY COOPERATION
              The Carriers will work together to secure the underlying
              governmental and other approvals necessary to implement this
              marketing relationship.

       D.     PUBLISHED FARES
              The carriers agree to participate in each others' published fares.

       E.     PRORATES                 (Attachment 3)
              ZK and UA will provide access to each other's system by
              maintaining the current standard prorate methodology
              (straight-rate proration) to support the overall program and to
              stimulate incremental traffic from ZK to UA, and UA to ZK. This
              will include special reciprocal protection for ZK or UA passengers
              on delayed, canceled or oversold flights.

       F.     FREQUENT FLYER           (Attachment 3)
              The Carriers shall participate in each other's frequent flyer
              programs. This participation will be exclusive as it relates to
              ZK's participation in the frequent flyer program of any U.S. based
              transportation company.

       G.     PREFERENTIAL SELLING
              The Carriers will implement procedures at their respective
              reservations sales offices to sell the other Carrier, on a "second
              to on-line" basis and in lieu of competitive off-line offerings in
              the agreed Code Share markets.

       H.     SALES
              With regard to Inventory Management for Code Share flights the
              Carriers acknowledge and agree that this Agreement does not
              provide for guaranteed block space reservations. Accordingly,
              neither UA nor ZK is purchasing or guaranteeing the seats
              allocated to it by the other. ZK and UA shall each manage, market
              and sell seats on the Code Share flights under its own respective
              airline designator code. The Carriers agree to communicate as
              necessary to facilitate such an arrangement, which will be
              phased-in in conjunction with ZK's purchase of automation
              equipment (CRS).

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       I.     JOINT SERVICE FEATURES           (Attachment 4)
              (1)    Fully Automated One-Stop Check-In
                     Both Carriers shall develop this capability using
                     international automated through check in (IATCI), to
                     provide passengers the convenience of checking in at
                     selected UA, UA Express, or ZK airport ticket counters and
                     receiving seat assignments, boarding cards, and Frequent
                     Flyer credit for their ZK/UA flights as appropriate. One
                     stop check-in also includes complete document verification
                     and baggage check to final destination.
              (2)    Improved Scheduling
                     The Carriers shall review their schedules to maximize, as
                     practicable, convenient connections to or from UA and ZK at
                     all common hubs in the U.S.
              (3)    Inflight Product Coordination
                     The Carriers shall evaluate the degree of coordination
                     required, including announcements, on code share flights.
              (4)    Seamless Transfer
                     The Carriers shall use reasonable efforts to expedite the
                     ransfer of all passengers and baggage between themselves,
                     as practicable, at all common hubs through development of a
                     shorter than standard connection time, including all
                     reasonable communications necessary to facilitate this
                     objective.
              (5)    Group Procedures
                     Groups shall be booked through each carrier's group desks.
              (6)    Air Cargo Service
                     The Carriers shall review cargo activities to investigate
                     what opportunities may exist to offer competitive and cost
                     effective air cargo services between points in the United
                     States. Further, ZK and UA shall cooperatively endeavor to
                     improve the quality of air cargo transportation to the
                     shipping community. The Carriers shall strive to sell the
                     other Carrier, on a "second to on-line" basis, and in lieu
                     of competitive off-line offerings.

       J.     DISTRIBUTION                     (Attachment 5)
              (1)    Display Improvement
                     To the extent permitted by applicable law and regulations,
                     UA and ZK shall provide preferential display of their
                     connecting flights in their respective internal reservation
                     systems and direct access displays provided through
                     computerized reservations systems.
              (2)    Quality Control
                     ZK and UA shall each use its best, commercially reasonable
                     efforts to ensure that the other party's flights, connect
                     points, fares, and rules both on-line and between ZK/UA are
                     included in each Carrier's respective host and affiliated
                     CRS system data base and are eligible for display subject
                     to system constraints and applicable laws and regulations.

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              (3)    Preferential Selling
                     The Carriers shall implement procedures at their respective
                     reservations sales offices to sell the other Carrier, on a
                     "second to on-line" basis and in lieu of competitive
                     off-line offerings in the agreed code share markets.

       K.     AIRCRAFT SECURITY
              The Carriers shall endeavor to agree upon a mutually satisfactory
              aircraft flight security program in accordance with FAA
              requirements.

5.     TERM
       This Agreement is effective as of May 1, 2001 and will continue
       thereafter for three (3) years; provided, however, that this Agreement
       may be terminated by either party at that party's election upon 360 days
       prior written notice.

6.     COMPLIANCE WITH GOVERNMENT AND SAFETY REQUIREMENTS
       A.     The Carriers represent and warrant that all air transportation
              services performed by it pursuant to this Agreement or otherwise
              will be conducted in full compliance with all applicable federal,
              state and local laws, statutes, orders, rules; and regulations.

       B.     The Carrier that originates the customer travel (provides all
              boarding passes and checks the customer luggage to his final
              destination) will assure that the customer is properly documented
              for entry into the destination country and properly documented for
              any transit points enroute. Any fines, penalties, deportation and
              detention expenses resulting from violations of government entry
              or transit requirements, even for passengers that willfully engage
              in illegal entry tactics, shall be the sole responsibility of the
              Carrier that originates the customer travel and such Carrier shall
              be considered an Operating Carrier pursuant to paragraph 15, and
              shall indemnify the other Carrier.

       C.     ZK represents and warrants that it has successfully undergone an
              FAA safety audit satisfactory to UA prior to ZK's execution of
              this Agreement and further warrants that it shall maintain
              compliance with the requirements of such audit. Any failure to
              maintain compliance shall immediately be brought to UA's attention
              along with corrective actions taken or a corrective action plan.
              Any non-compliance not promptly corrected to UA's satisfaction or
              repeated noncompliance shall be grounds for termination by UA
              without further liability, but with reservation of all other
              rights and remedies available to UA. Additional safety review
              audits may be required at UA's discretion and ZK shall cooperate
              with all such audits.

7.     EXCLUSIVITY
       This Agreement is non-exclusive and does not preclude either UA or ZK
       from entering into or maintaining existing marketing relationships,
       including code sharing, with other Carriers. Notwithstanding the
       preceding sentence, this agreement is exclusive as it

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       relates to each Carrier's participation in code sharing, on the flights
       described in Attachment 1.

8.     TRADEMARKS
       Neither Carrier will use any trademark, trade name, logo, or service mark
       of the other without the prior written consent of the other.

9.     CONFIDENTIALITY
       A.     Subject to Articles 9B, 9C and 9D, and except in any proceeding to
              enforce any of the provisions of this Agreement, neither party
              will, without the prior written consent of the other, use,
              publicize or disclose to any third party, either directly or
              indirectly, any of the following (hereinafter "Confidential
              Information"):
              (1)    this Agreement or any of the terms or conditions of this
                     Agreement; or
              (2)    any confidential or proprietary information or data, either
                     oral or written, received from and designated as such by
                     the disclosing Carrier.

       B.     If either Carrier is served with a subpoena or other legal process
              requiring the production or disclosure of any Confidential
              Information, then that Carrier, before complying, will immediately
              notify the non-disclosing Carrier and the non-disclosing Carrier
              shall have a reasonable period of time to intervene and contest
              disclosure or production.

       C.     If a governmental authority requests either Carrier to produce or
              disclose to the authority this Agreement or any of the terms or
              conditions of this Agreement, or if any governmental regulatory
              agency (e.g., SEC or DOT) requires the production or disclosure of
              this Agreement or its terms, such Carrier, at its option and after
              notifying the other Carrier, may produce or disclose the requested
              document or information.

       D.     If any financial institution requests or requires production or
              disclosure of this Agreement or its terms, ZK and UA may produce
              or disclose this Agreement provided the financial institution
              agrees to keep the disclosed material and information
              confidential.

       E.     Upon termination of this Agreement, all Confidential Information,
              including any copies thereof made by the receiving party, must be
              returned to the disclosing Carrier.

10.    FORCE MAJEURE
       Neither Carrier will be liable for delays or failure in performance under
       this Agreement caused by acts of God, war, strikes, labor disputes, work
       stoppage, fire, acts of government or any other cause, whether similar or
       dissimilar, which is beyond the control of that Carrier.

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11.    NATURE OF RELATIONSHIP BETWEEN ZK AND UA
       The relationship of the Carriers hereto is that of independent
       contractors. Nothing in this Agreement is intended or shall be construed
       to create or establish any partnership or joint venture relationship
       between the Carriers.

12.    TERMINATION FOR CAUSE
       A.     If either Carrier (the "Defaulting Party") becomes insolvent or is
              subject to liquidation, composition with creditors, reorganization
              or bankruptcy; if the other Carrier (the "Insecure Party") has
              evidence that the Defaulting Party is not paying its bills when
              due without just cause; if the Defaulting Party takes any step
              leading to its cessation as a going concern; or if the Defaulting
              Party either ceases or suspends operations for reasons other than
              Force Majeure, then the Insecure Party may immediately terminate
              this Agreement on notice to the Defaulting Party unless the
              Defaulting Party immediately gives adequate assurance of the
              future performance of this Agreement by establishing an
              irrevocable letter of credit issued by an bank acceptable to the
              Insecure Party, on terms and conditions acceptable to the Insecure
              Party, in an amount sufficient to cover all amounts potentially
              due from the Defaulting Party under this Agreement, which may be
              drawn upon by the Insecure Party if the Defaulting Party does not
              fulfill its obligations under this Agreement in a timely manner.

       B.     If either Carrier (the "Defaulting Party") fails to observe or
              perform any of its material obligations under this Agreement and
              if this failure continues for a period of thirty (30) days after
              written notice to the Defaulting Party thereof (except for any
              payments due, where the period to cure such non-payment will be
              five [5] days after notice) then, without prejudice to any other
              rights or remedies the other party may have, the other Carrier may
              terminate this Agreement as of the expiration date of this notice
              period.

13.    POST-TERMINATION RIGHTS
       Exercise by either Carrier of its right to terminate under any provision
       of this Agreement will not affect or impair its right to enforce its
       other rights or remedies under this Agreement. All obligations of each
       Carrier that have accrued before termination or that are of a continuing
       nature will survive termination, including, without limitation, any
       confidentiality and indemnity provisions.

14.    NON-WAIVER
       Any previous waiver, forbearance, or course of dealing will not affect
       the right of either Carrier to require strict performance of any
       provision of this Agreement.

15.    GENERAL INDEMNIFICATION
       The Carrier operating the Code Share flight or providing goods or
       services hereunder (the "Operating Carrier") agrees to indemnify and hold
       harmless the other Carrier (the "Marketing Carrier"), its directors,
       officers, employees, agents, subcontractors, and affiliates (each an
       "Indemnitee") from and against any and all liabilities, claims, demands,
       suits, damages, and losses, including, without limitation, all reasonable
       attorneys' fees, costs and expenses in connection therewith or incident
       thereto (including, without

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       limitation, attorneys' fees incurred by the Marketing Carrier in
       establishing its right to indemnification hereunder) (collectively
       referred to in this Article as "Claims") of third parties for death or
       personal injury to any person or persons whomsoever (including, without
       limitation, the Operating Carrier's employees, but excluding the
       Marketing Carrier's employees) and for loss of, damage to, destruction
       of, any property whatsoever (including, without limitation, any loss of
       use thereof), in any manner arising out of or in any way connected with
       goods or services furnished or to be furnished by the Operating Carrier
       under this Agreement, all whether or not arising in tort or occasioned in
       whole or in part by the negligence of the Marketing Carrier of any type
       or degree. The Operating Carrier shall, at the request of the Marketing
       Carrier, negotiate and defend any Claim brought against any Indemnitee or
       in which any Indemnitee is joined as a party defendant based upon any
       other matters for which the Operating Carrier has agreed to indemnify
       each Indemnitee as provided above. The Operating Carrier's obligations
       under this Article will survive the expiration or termination of this
       Agreement.

16.    INSURANCE

       A.     (1) UA shall procure and maintain (i) third party liability
              insurance for a minimum combined single limit (bodily
              injury/property damage) of U.S. $300,000,000 (three hundred
              million U.S. dollars) for each occurrence and (ii) Hull All Risks
              and Hull War Risks insurance covering its fleet. ZK shall be named
              as additional insured on UA's policies when UA is acting as the
              Operating Carrier (the "Operating Carrier"). UA, as Operating
              Carrier, shall waive their rights of subrogation against ZK. The
              insurance policies shall be endorsed with severability of interest
              clauses. UA shall furnish to ZK certificates of insurance
              evidencing the foregoing coverage prior to the commencement of
              this Agreement.

              (2) ZK shall procure and maintain (i) third party liability
              insurance for minimum combined single limit (bodily
              injury/property damage) of U.S. $300,000,000 (three hundred
              million U.S. dollars) for each occurrence and (ii) Hull All Risks
              and Hull War Risks insurance covering its fleet. UA shall be named
              as additional insured on ZKs policies when ZK is acting as the
              Operating Carrier. ZK, as Operating Carrier, shall waive their
              rights of subrogation against UA. The insurance policies shall be
              endorsed with severability of interest clauses. ZK shall furnish
              to UA certificates of insurance evidencing the foregoing coverage
              prior to the commencement of this Agreement.

       B.     ZK and UA shall each procure at its own cost employer's liability
              insurance and worker's compensation (or equivalent) against the
              liabilities of each respective Carrier to its employees in an
              amount not less than required by applicable law.

       C.     In the event of cancellation or adverse material change, the
              additional insured shall be provided not less than thirty (30)
              days prior written notice except that in the case of Hull War
              Risks insurance such period of notice shall be seven (7) days or
              such lesser period as may be available in accordance with the
              applicable insurance policy requirements.

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17.    EXCLUSION OF CONSEQUENTIAL DAMAGES
       NEITHER CARRIER WILL BE LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL OR
       CONSEQUENTIAL DAMAGES, INCLUDING LOST REVENUES, LOST PROFITS, OR LOST
       PROSPECTIVE ECONOMIC ADVANTAGE, WHETHER OR NOT FORESEEABLE AND WHETHER OR
       NOT BASED ON CONTRACT, TORT, WARRANTY CLAIMS OR OTHERWISE IN CONNECTION
       WITH THIS AGREEMENT, AND/OR THE PRODUCTS OR SERVICES PROVIDED HEREUNDER,
       AND EACH CARRIER HEREBY RELEASES AND WAIVES ANY CLAIMS AGAINST THE OTHER
       CARRIER REGARDING SUCH DAMAGES.

18.    NOTICES
       Any notices required to be sent under this Agreement will be sent by
       first class mail, postage prepaid, or any more expedient written means.

       If to ZK, notices will be addressed as follows:

                    Great Lakes Aviation, Ltd.
                    1022 Airport Parkway
                    Cheyenne, Wyoming 82001

                    Attn:  Doug Voss, President

       If to UA, notices will be addressed as follows:

                    United Air Lines, Inc.
                    P.O. Box 66100
                    Chicago, Illinois 60666
                    Attn:  Vice President - Alliances

       Notices sent via electronic means (e.g., telex, facsimile) will be
       effective immediately if received prior to 5:00 p.m. local time of the
       recipient. All other notices will be effective the first business day
       after receipt.

19.    GOVERNING LAW
       This Agreement and any dispute arising under or in connection with this
       Agreement, including any action in tort, will be governed and construed
       by the laws of the State of Illinois U.S.A., without regard to any
       conflict of laws principles which may direct the application of laws of
       any other jurisdiction.

20.    SEVERABILITY
       Each provision of this Agreement shall be valid and enforced to the
       furthest extent permitted by law. The invalidity or unenforceability of
       any provision of this Agreement shall not affect the validity or
       enforceability of any other provision.

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21.    ASSIGNMENT AND CHANGE OF OWNERSHIP
       A.     Neither Carrier may assign or otherwise transfer any of its rights
              or obligations under this Agreement to any third party without the
              prior written consent of the other.

       B.     Should for any reason whatsoever the ownership of either Carrier
              change such that another air carrier or affiliate of an air
              carrier acquires a ten percent (10%) or more ownership interest in
              either party, then within thirty (30) days of such occurrence
              either party may request renegotiation of this Agreement and,
              failing successful renegotiation within sixty (60) days of the
              request to renegotiate, either party may terminate this Agreement
              upon thirty (30) days notice to the other party.

22.    ENTIRE AGREEMENT
       This Agreement, the Transition Agreement and the various side letters
       issued pursuant to this Agreement, including any and all Attachments,
       constitute the entire agreement and understanding of the Carriers
       relating to the subject matter hereof, and supersedes all prior
       agreements, whether oral or written, express or implied, between the
       Carriers concerning the subject matter hereof. In the event that any
       terms herein conflict with the terms of any interline or other agreement
       between the Carriers, then the terms herein shall prevail, but shall not
       supplant any conflicting terms in the other agreement. This Agreement may
       be modified only by further written agreement signed by all of the
       Carriers hereto.

23.    EXISTING OBLIGATIONS
       UA represents and warrants that the terms of this Agreement do not
       violate any existing obligations or contracts of UA. ZK represents and
       warrants that the terms of this Agreement do not violate any existing
       obligations of ZK. Each Carrier shall defend, indemnify and hold the
       other harmless from and against any and all claims, demands or causes of
       action which are hereafter made or brought against it alleging any such
       violation.

24.    PERFORMANCE MEASURES                        (Attachment 6)
       ZK agrees to provide UA, monthly, with performance measures that UA will
       use to evaluate if ZK is providing service at a level that meets
       pre-determined standards, as set forth in Attachment 6. Any failure to
       maintain these standards shall immediately be brought to UA's attention
       along with corrective actions taken or a corrective action plan. Any
       non-compliance not promptly corrected to UA's satisfaction or repeated
       non-compliance shall be grounds for termination by UA without further
       liability, but with reservation of all other rights and remedies
       available to UA, provided, however, that ZK's failure to maintain
       performance standards shall not constitute grounds for termination if
       ZK's failure to perform is due to the relevant and material fault of UA.

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IN WITNESS WHEREOF, the Carriers hereto have by their duly authorized officers
executed this Agreement as of the dates set forth below.

    GREAT LAKES AVIATION, LTD.                     UNITED AIR LINES, INC.


By:  /s/ Doug G. Voss                    By:   /s/ Rono Dutta
   ----------------------------------       ------------------------------------

Name       Douglas G. Voss                           Rono Dutta

Title:     President and CEO                         President

Date: February 1, 2001                   Date: January 31, 2001

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                                  ATTACHMENT 1

                                  CODE SHARING

A.   City pairs displayed as UA*

          Subject to all necessary regulatory approvals, deployment of IATCI One
          Stop Check-In, and completion of necessary operational support
          arrangements, UA shall display its UA designation code on selected
          flights, operated by ZK, provided, however, that UA may remove, and ZK
          may stop carrying, the UA designation from any flights, upon 360 day's
          written notice:

                     ZK Operated Flights Between Chicago and

                              Chicago-Based Cities
                              Dubuque, IA
                              Muskegon, MI
                              Springfield, IL
                              Waterloo, IA
                              Iron Mountain, MI
                              Manistee, MI
                              Oshkosh, WI
                              Ottumwa, IA

                     ZK Operated Flights Between Denver and

                              Denver-Based Cities
                              Alamosa, CO
                              Alliance, NE
                              Amarillo, TX
                              Casper, WY
                              Chadron, NE
                              Cheyenne, WY
                              Cody, WY
                              Cortez, CO
                              Dickinson, ND
                              Dodge City, KS
                              Farmington, NM
                              Garden City, KS
                              Gillette, WY
                              Grand Island, NE
                              Gunnison, CO
                              Hayden, CO
                              Hays, KS

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                              Kearney, NE
                              Laramie, WY
                              Liberal, KS
                              Moab, AZ
                              McCook, NE
                              Norfolk, NE
                              North Platte, NE
                              Page, AZ
                              Phoenix, AZ
                              Pierre, SD
                              Pueblo, CO
                              Riverton, WY
                              Rock Springs, WY
                              Salina, KS
                              Santa Fe, NM
                              Scottsbluff, NE
                              Sheridan, WY
                              Telluride, CO
                              Vernal, UT
                              Williston, ND
                              Worland, WY
                              Yankton, SD

B.   Inventory Management

          The Carriers shall establish mutually agreed inventory management
          procedures for Code Share flights, in accordance with the guidelines
          outlined in Article 4 of this agreement ("Programs"), and including
          for manually managed inventory allocations the areas for cooperation
          outlined in Attachment 1A.

          TO BE COMPLETED BY January 31, 2002

          Action:

                ZK   Dick Fontaine    HDQSCZK    (307) 432-7020
                UA   Elisabeth Mach   HDQIMUA    (847) 700-6277

C.   Code Share Schedule Operations

The Carriers will:

     (1)  establish a dedicated flight number range for use by ZK and UA on Code
          Share flights.

     (2)  establish an automated transfer of flight schedule information via an
          industry standard SSIM which includes comment 10 and 50 records to
          identify the Code

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          Share relationships. A "custom SSIM" from ZK will be used in place of
          the OAG file to maintain ZK's schedule in the Apollo and Galileo
          computer reservation systems.

     (3)  establish a communications procedure to advise the other of passenger
          reaccommodation plans in the event of schedule changes involving a
          Code Share flight.

     TO BE COMPLETED BY January 31, 2002.

          Action:

                 ZK     Dick Fontaine    HDQSCZK     (307) 432-7020

                 UA     Tina Drzal       HDQRLUA     (847) 700-5020

D.   Interline Accounting

          The Carriers shall establish all necessary accounting procedures, in
          accordance with applicable IATA or ACH guidelines, including sampling
          methodology, to facilitate settlement of all UA/ZK interline
          transportation, including code share.

TO BE COMPLETED BY January 31, 2002.

          Action:

                 ZK     Teresa Henry     HDQRAZK     (307) 432-7040

                 UA     Bob Portschy     HDQANUA     (847) 700-1601

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                                  ATTACHMENT 1A

                        BUSINESS REQUIREMENTS CODE SHARE

TABLE OF CONTENTS

1.0  OVERVIEW

     1.1  Introduction

     1.2  Objective

2.0  REQUIREMENTS

     2.1  Availability

     2.2  Booking/Ticketing/CRS Fees

          2.2.1   Sell
          2.2.2   Disclaimer
          2.2.3   Group Handling
          2.2.4   Teletype (TTY)
          2.2.5   Customer Inquiries

     2.3  Inventory Maintenance

          2.3.1   Inventory Control
          2.3.2   Link Sells
          2.3.3   Waitlist

     2.4  Through Check In

     2.5  Schedule Maintenance

          2.5.1   Schedule Dissemination
          2.5.2   Schedule Change
          2.5.3   Passenger Reaccommodation
          2.5.4   Seat Reaccommodation

     2.6  Accounting Systems

     2.7  Frequent Flyer

3.0  Hardware

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1.0  OVERVIEW

          The purpose of this Attachment 1A is to provide a method that will
          allow UA's code to be reflected on certain ZK flights. Each Carrier
          shall perform this procedures in a fully automated manner, or manually
          until a fully automated method can be implemented.

2.0  REQUIREMENTS

     General Requirement

     Support code share for the city pairs as set forth on Attachment 1,
     paragraph A.

     2.1  Availability

          The Carrier shall provide the capability to display the service as an
          on-line connection using the designated Carrier's code (UA).

     2.2  Booking/Ticketing/CRS Fees

          2.2.1   Sell

                  The Carriers shall provide support for segment sell of the
                  on-line connection by line number from availability.

                  The Carriers shall provide support for the manual sell of the
                  connection using either the code share flight number or the
                  base flight number.

                  The Carriers shall provide for any fees associated with either
                  ticket handling fees or CRS fees related to transportation of
                  a passenger to be paid, by segment, by the Operating Carrier.
                  ZK and UA will establish a process to ensure that all such
                  fees are appropriately accounted for. The Operating Carrier
                  will be responsible for CRS fees at the level of participation
                  of the Marketing Carrier.

                  In this connection, the Marketing Carrier will be obligated to
                  provide the Operating Carrier only the CRS vendor's invoice
                  and the CRS vendor's generated microfiche or hard copy of
                  bookings for flights of Operating Carrier, and the Operating
                  Carrier must reimburse the Marketing Carrier based upon the
                  data reflected in those documents without adjustment.

          2.2.2   Disclaimer

                  The Carriers shall provide for a disclaimer to accompany a
                  sell of a shared-code flight identifying the Carrier operating
                  the flight. The

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<PAGE>

             disclaimer must be distributed to CRS's and to schedule
             dissemination services such as the Official Airline Guide (OAG).

     2.2.3   Group Handling

             Groups will be booked through each Carrier's group desk.

     2.2.4   Teletype (TTY)

             Teletype processing will be handled for UA or ZK designated flights
             as it is currently handled today.
             The information will be updated within the PNR of the respective
             system automatically and will be passed with the PNR on the
             exchange of PNRs.

     2.2.5   Customer Inquiries

             Procedures will be established through the reservations groups to
             be able to identify where a PNR exists and be able to direct the
             customer appropriately.

2.3  Inventory Maintenance

     2.3.1   Inventory Control

             The operating Carrier will develop a method for inventory control
             on each Code Share flight to/from the designated cities and will
             maintain control of that inventory. The designated Carrier will
             create a pseudo flight with the appropriate inventory. The yield
             management groups of both Carriers will agree on the following:

                  - A method of managing inventory allocations on shared-code
                    flights.

                  - Actual allocation of agreed number of seats by cabin.

                  - Close off and transfer of PNRs, at a minimum 24 hours prior
                    to departure of shared-code flights.

                  - For manually managed inventory allocations, exchange of
                    industry standard PNL's, at a maximum 72 hours prior to
                    departure, and ADL's at a mutually agreed time prior to
                    departure, of shared code flights.

                  - Class of service and class of service equivalency

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                 - A communications procedure to allow ad hoc inventory changes
                   and to ensure that unused inventory is released or
                   transferred.

     2.3.2 Link Sells

           Allow a shared-code flight to be sold from an availability display
           provided to another Carrier.

     2.3.3 Waitlist

           Waitlists will be open at start up of the Code Share arrangement.

2.4  Through Check In

     Provide the capability to through-check customers via the use of IATCI
     standards.

2.5  Schedule Maintenance

     2.5.1 Schedule Dissemination

           Each Carrier will establish an automated transfer of flight schedule
           information via an industry standard SSIM which includes comment 10
           and 50 records to identify the Code Share relationships. A "custom
           SSIM" from ZK will be used in place of the OAG file to maintain ZK's
           schedule in the Apollo and Galileo computer reservation systems.

     2.5.2 Passenger Reaccommodation

           Reaccommodations will be worked through close coordination between
           the reservations groups of the two Carriers.

     2.5.3 Flight Information

           ZK and UA will evaluate procedures for exchanging and updating FLIFO
           information in each other's systems. Procedures and responsibility
           will be determined and mutually agreed by the Carriers.

2.6  Accounting Systems

     Accounting based on billing is currently handled on a manual basis for bank
     Air Lines flights and does not create any new issues. Any special prorates
     must be communicated to accounting to ensure proper billing.

                                       17

<PAGE>

     2.7   Frequent Flyer

           Procedures for providing automated accrual and redemption will be
           established by respective Frequent Flyer organizations.

3.0  Hardware

           Each Carrier will provide and pay for installation and maintenance of
           computer equipment necessary for the other to support Code Share
           operations. This equipment may include, but is not limited to
           check-in terminals, boarding pass printers and bag tag printers. Any
           monthly charges associated with such equipment will be paid by the
           Carrier supplying said equipment.

           Upon termination of Code Share operations, for any reason, the
           Carriers will return any equipment owned by the other party.

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<PAGE>

                                  ATTACHMENT 2

                         CODE SHARE EMERGENCY PROCEDURES

In order to properly prepare and plan coordinated communications efforts between
the Carriers in the event of an emergency, as defined below, involving a Code
Share flight, both Carriers will (i) exchange and update the appropriate
telephone numbers and SITA addresses of the operating Carrier to which the code
sharing Carrier may refer customer/relative inquiries in the event of an
emergency and (ii) discuss any other necessary coordinated emergency response
procedures. Although each situation must be evaluated on its own merit, common
sense must prevail as a guide for all parties to follow.

Definitions:

-Emergency

Any occurrence involving a Code Share flight that results in injury or death, or
has the potential for injury or death to any person or the loss or damage or the
potential for loss or damage to private, public, or Carrier property.

-Aircraft Accident

Any occurrence associated with the operation of an aircraft, which takes place
between the time the captain has released the parking brake for pushback or taxi
and has set the parking brake and all checklists are completed, in which any
person who has boarded the aircraft with the intention of flight suffers death
or serious injury or in which an aircraft receives substantial damage.

-Hijacking (Air Piracy)

Any seizure or exercise of control by force or violence, or threat of violence,
and with wrongful intent of an aircraft in air commerce.

-Red Alert

The classification for a situation where a major problem exists that may result
in an accident as defined above. Examples include a landing gear failure to
extend, fire in flight, or other aircraft damage that will likely require
outside agencies such as police, fire, ambulances, and physicians to respond.

Both Carriers agree to comply with the relevant requirements of government
agencies having jurisdiction in respect of an Emergency, Aircraft Accident,
Hijacking or Red Alert.

Appropriate UAL telephone numbers in the event of an emergency as described
above:

     UAL Shift Manager (24 Hours)
     847 700-6295                      (Phone)
     847 700-2005                      (FAX)
     HDQOPUA                           (SITA Address)

Appropriate ZK telephone numbers in the event of an emergency as described
above:

     ZK Shift Manager   (24 Hours)
     307-432-7222       (Phone)
     307-432-7221       (FAX)
     HDQOOZK            (SITA Address)

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<PAGE>

Any change to the above referenced phone numbers or contacts is to be
communicated to the above referenced SITA addresses with a request for a
confirming telex back to the originator to acknowledge receipt.

B.  EMERGENCY PLAN

    (1)  The Carriers mutually agree to subscribe to the IATA Standards and
         Recommended Practices for the Assistance of Survivors and Families of
         Passengers in the Aftermath of an Aircraft Accident or Incident.

    (2)  In addition to the aforementioned procedures, the Carriers will meet
         and endeavor to mutually agree on a detailed emergency plan.

TO BE COMPLETED BY January 31, 2002

    Action:

           ZK  Dick Nelson    HDQSCZK       (307) 432-7210
           UA  Jim Konz       HDQCSUA       (847) 700-5133

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<PAGE>

                                  ATTACHMENT 3

                       PRORATES AND FREQUENT FLYER PROGRAM

A.     Prorates

       ZK and UA shall provide access to each other's system by maintaining the
       current standard prorate methodology (straight rate proration) to support
       the overall program and to stimulate incremental traffic from UA to ZK,
       and ZK to UA.

       TO BE COMPLETED FOR IMPLEMENTATION, AS MUTUALLY AGREED, EFFECTIVE January
       31, 2002

       Action:

                    ZK       Teresa Henry       HDQRAZK        (307) 432-7040

                    UA       Yvonne Fox         HDQNCUA        (847) 700-4963

B.     Frequent Flyer Program

       ZK and UA shall implement mutually beneficial programs to enhance ZK/UA
       passenger loyalty including, as follows:

       .      Handling of Frequent Flyer accrual information on ZK and UA
              flights to provide consistency.

       .      Accrual and redemption levels to be charged by each Carrier for
              travel by its Frequent Flyer members on code share sectors
              operated by the other.

       IMPLEMENTATION PLAN, AS APPROPRIATE, TO BE COMPLETED FOR IMPLEMENTATION
       ON January 31, 2002.

       Action:

                    ZK        Dick Fontaine     HDQSCZK        (307) 432-7020
                    UA        Lou Brigham       HDQPRUA        (847) 700-7692


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<PAGE>

                                  ATTACHMENT 4

                             JOINT SERVICE FEATURES

A.     Automated One Stop Check-In

       When the UA/ZK codeshare arrangement becomes operational, both Carriers
       shall have developed, tested, and implemented fully automated One Stop
       Check-In. Services rendered shall include:

                        -    Seat Assignments
                        -    Boarding Cards
                        -    Frequent Flyer Credit
                        -    Baggage Check to final destination

       for up to three segments under each Carrier's designator code, for a
       maximum of six (6) segments (five connecting points). Segments under the
       "UA" designator code may include flights operated by UA Express Carriers.

       TO BE IMPLEMENTED BY January 31, 2002 FOR THE CITY PAIRS AS SET FORTH ON
       ATTACHMENT 1, PARAGRAPH A AND B OF THE CODE SHARE AND REGULATORY
       COOPERATION AGREEMENT.

       Action:

                    ZK       Jim Frazier        HDQSCZK        (307) 482-7270
                    UA       Brett Anderson     DENKAUA        (303) 779-7081


B.     Improved Connection Scheduling

       (1)    Each Carrier shall complete a review of all practical ZK/UA
              schedule improvement possibilities at all common gateways.

       (2)    Each Carrier shall establish a plan for ongoing, regularly
              scheduled reviews to optimize future schedule changes by either
              party.

       TO BE COMPLETED BY January 31, 2002.

       Action:

                    ZK       Dick Fontaine      HDQSCZK        (307) 432-7020
                    UA       Tim Drzal          HDQASUA        (847) 700-5020


                                       22

<PAGE>

C.     Inflight Service Coordination

       The Carriers shall establish a forum to exchange ideas and suggestions on
       Inflight Services to help provide consistency for the customer.

       TO BE COMPLETED BY January 31, 2002, FOR IMPLEMENTATION by the first day
       of operation of the codeshare - to be determined.

       Action:

                    ZK       Dick Nelson        HDQSCZK        (307) 432-7210
                    UA       Arlene Johnson     HDQSWUA        (847) 700-3592

D.     Seamless Transfer Service

       The Carriers shall evaluate and develop proactive procedures and identify
       facilities to be used to ensure expeditious check-in and transfer of
       passengers and baggage between the respective services at all common
       hubs. Areas for review and coordination include:

       (1)    Support for connecting passengers and baggage

       (2)    Information and directional signage to assist customers

       (3)    Security procedures as governmentally required

       TO BE COMPLETED FOR IMPLEMENTATION BEGINNING ON January 31, 2002.

       Action:

                    ZK       Jim Frazier        HDQSCZK        (307) 432-7270
                    UA       James Gabriel      HDQCSUA        (847) 700-5393

E.     Group Procedures

       Groups shall be booked through each Carrier's group desk.

       Contacts:

                    ZK       Pam Flynn          HDQSCZK        (307) 432-7295
                    UA       Pat Snelling       HDQRRUA        (313) 234-6937


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<PAGE>

F.     Air Cargo Service

       ZK and UA shall review and implement, as agreed, programs including
       prorates, booking and inventory capabilities, and joint trade show
       participation.

                    ZK       Brent Skillman     HDQSCZK        (612) 889-9329
                    UA       Michael Stacy      HDQSAUA        (847) 700-5637

       TO BE COMPLETED FOR IMPLEMENTATION BEGINNING ON January 31, 2002


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<PAGE>

                                  ATTACHMENT 5

                             DISTRIBUTION/AUTOMATION

A.     Display Improvement

       To the extent permitted by applicable law and regulations, UA and ZK
       connections shall receive preference in the Carrier specific display
       option or direct access programs either UA or ZK has with any other
       computer reservation systems used by travel agents, corporate accounts,
       or any non-airline staff for the purpose of making airline reservations,
       or internal displays.

       TO BE COMPLETED BY January 31, 2002.

       Action:

                    ZK       Pam Flynn          HDQSCZK        (307) 432-7295
                    UA       George Tyms        HDQIMUA        (847) 700-5667

B.     Quality Control

       ZK and UA shall each use its best, commercially reasonable efforts to
       ensure that the other party's flights, connect points, fares, and rules
       both on-line and between ZKJUA are included in each Carrier's respective
       host and affiliated CRS system data base and are eligible for display
       subject to system constraints and applicable laws and regulations.

       TO BE COMPLETED BY January 31, 2002.

       Action:

                    ZK       Pam Flynn          HDQSCZK        (307) 432-7295
                    UA       George Tyms        HDQIMUA        (847) 700-5667

C.     Preferential Selling/Reservation Sales

       ZK and UA shall implement programs and incentives to motivate key ZK and
       UA reservations to reciprocally sell their code share products, on a
       "second to on-line" basis.

       TO BE COMPLETED FOR IMPLEMENTATION BY January 31, 2002.

       Action:

                    ZK       Dick Fontaine      HDQSCZK        (307) 432-7020
                    UA       Teri Hartwig       HDQRZUA        (847) 700-5942


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<PAGE>

                                  ATTACHMENT 6

                              PERFORMANCE MEASURES

ZK shall provide monthly results of its performance, system-wide, to UA, and
shall meet the minimum performance standards as follows, or meet the performance
standards as reported by UA for Denver for the same period and operational
categories, whichever is lower:

..      Flight Schedule Departure Completion (excluding weather and ATC):  98.0%
..      On-time departures as scheduled (zero)                             56.0%

ZK agrees to ensure that this information is accumulated and maintained in such
a manner that it can be readily audited for accuracy by representatives of UA.
UA, or its representatives, shall have the right to audit such information at
any reasonable time at the location where the records are maintained by ZK.

       Action:

                    ZK       Dick Nelson        HDQSCZK        (307) 432-7210
                    UA       Dennis Berry       HDQNCUA        (847) 700-9378

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