Document:

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                                                                     EXHIBIT 4.2

                                                                  Execution Copy

                              FIRST AMENDMENT TO CREDIT AGREEMENT

               THIS FIRST AMENDMENT TO CREDIT AGREEMENT, dated as of September
30, 1998 (this "Amendment"), is among AIRNET SYSTEMS, INC., an Ohio corporation
(the "Company"), the lenders set forth on the signature pages hereof
(collectively, the "Lenders") and NBD BANK, a Michigan banking corporation, as
agent for the Lenders (in such capacity, the "Agent").

                                    RECITALS

               The Company, the Agent and the Lenders are parties to a Credit
Agreement, dated as of August 1, 1998 (the "Credit Agreement"). The Company
desires to amend the Credit Agreement, and the Agent and the Lenders are willing
to do so strictly in accordance with the terms hereof.

                                      TERMS

               In consideration of the premises and of the mutual agreements
herein contained, the parties agree as follows:

ARTICLE 1.
                                   AMENDMENTS

               Upon fulfillment of the conditions set forth in Article 3 hereof,
the Credit Agreement shall be amended as follows:

The following new definition is hereby added to Section 1.1 in appropriate
alphabetical order:

               "Significant Subsidiary" shall mean any one or more Subsidiaries
which, if considered in the aggregate as a single Subsidiary would be a
"significant subsidiary" as defined in Rule 1-02 of Regulation S-X under the
Exchange Act, provided that no Subsidiary which is not by itself a Significant
Subsidiary shall be included in any Significant Subsidiary if all Subsidiaries
which are not by themselves Significant Subsidiaries or Guarantors would not
constitute a Significant Subsidiary.

Reference in the definition of "Guarantors" contained in Section 1.1 and in the
third line of Section 5.1(f) to "Subsidiary" shall be deleted and "Significant
Subsidiary" shall be substituted in each place thereof.

Section 5.2(a) is amended by deleting reference therein to "$70,000,000" and
substituting "$65,000,000" in place thereof.

ARTICLE 2.
                                   GUARANTIES

The Company has requested that the Lenders defer the requirement under the
Credit Agreement of all of the Significant Subsidiaries of the Company executing
and delivering a Guaranty to the Agent and the Lenders together with
resolutions, legal opinions and corporate documents in connection with such
Guaranty. In accordance with such request, the Lenders and the Company agree
that any Significant Subsidiaries of the Company, if any, existing as of the
date of this Amendment, will not be required to deliver a Guaranty and the
resolutions, legal opinions and corporate documents required by the Agent in
connection therewith until December 31, 1998.

ARTICLE 3.
                                 REPRESENTATIONS

               The Company represents and warrants to the Agent and the Lenders
that:

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        3.1 The execution, delivery and performance of this Amendment are within
its powers, has been duly authorized and is not in contravention with any law,
of the terms of its Articles of Incorporation or By-laws, or any undertaking to
which it is a party or by which it is bound.

        3.2 This Amendment is the legal, valid and binding obligations of the
Company enforceable against it in accordance with the terms hereof.

        3.3 After giving effect to the amendments herein contained, the
representations and warranties contained in Article IV of the Credit Agreement
are true on and as of the date hereof with the same force and effect as if made
on and as of the date hereof.

        3.4    No Event of Default or Default exists or has occurred and is
continuing on the date hereof.

ARTICLE 4.
                                 MISCELLANEOUS.

        4.1 This Amendment shall not become effective until this Amendment shall
be signed by the Company, the Agent and the Required Lenders.

        4.2 References in the Credit Agreement or in any note or other Loan
Document to the Credit Agreement shall be deemed to be references to the Credit
Agreement as amended hereby and as further amended from time to time.

        4.3 Except as expressly amended hereby, the Company agrees that the
Credit Agreement, the Notes and all other documents and agreements executed by
the Company in connection with the Credit Agreement in favor of the Agent or any
Lender are ratified and confirmed and shall remain in full force and effect and
that it has no set off, counterclaim or defense with respect to any of the
foregoing. Terms used but not defined herein shall have the respective meanings
ascribed thereto in the Credit Agreement.

        4.4 This Amendment may be signed upon any number of counterparts with
the same effect as if the signatures thereto and hereto were upon the same
instrument.

               IN WITNESS WHEREOF, the parties signing this Amendment have
caused this Amendment to be executed and delivered as of the day and year first
above written.

                              AIRNET SYSTEMS, INC.

                              By: _________________________________

                                  Its: ____________________________

                              NBD BANK, as Agent and as a Lender

                              By: _________________________________

                                  Its: ____________________________

                              BANK ONE, N.A.

                              By: _________________________________

                                  Its: ____________________________

                              KEYBANK NATIONAL ASSOCIATION

                              By: _________________________________

                              Its: ________________________________

                                       2<PAGE>

                                                                    EXHIBIT 4.3

                      SECOND AMENDMENT TO CREDIT AGREEMENT

               THIS SECOND AMENDMENT TO CREDIT AGREEMENT, dated as of December
31, 1999 (this "Amendment"), is among AIRNET SYSTEMS, INC., an Ohio corporation
(the "Company"), the lenders set forth on the signature pages hereof
(collectively, the "Lenders") and BANK ONE, MICHIGAN, a Michigan banking
corporation formerly known as NBD Bank, as agent for the Lenders (in such
capacity, the "Agent").

                                     RECITAL

               The Company, the Agent and the Lenders are parties to a Credit
Agreement, dated as of August 1, 1998, as amended by the First Amendment to
Credit Agreement dated as of September 30, 1998 (as same may be amended or
modified from time to time, the "Credit Agreement"). The Company desires to
amend the Credit Agreement, and the Agent and the Lenders are willing to do so
strictly in accordance with the terms hereof.

                                      TERMS

               In consideration of the premises and of the mutual agreements
herein contained, the parties agree as follows:

ARTICLE 1.
                                   AMENDMENTS

               Upon fulfillment of the conditions set forth in Article 2 hereof,
the Credit Agreement shall be amended as follows:

Section 5.2(f) is amended and restated in its entirety as follows:

                      (f) Disposition of Assets; Etc. Sell, lease, license,
               transfer, assign or otherwise dispose of any of its business,
               assets, rights, revenues or property, real, Personal or mixed,
               tangible or intangible, whether in one or a series of
               transactions, other than inventory sold in the ordinary course of
               business upon customary credit terms and sales of scrap or
               obsolete material or equipment, provided, however that this
               Section 5.2(f) shall not prohibit (i) any such sale, lease,
               license, transfer, assignment or other disposition if the
               aggregate book value (disregarding any write-downs of such book
               value other than ordinary depreciation and amortization) of all
               of the business, assets, rights, revenues and property disposed
               of after the date of this Agreement shall be less than $3,500,000
               in the aggregate for any calendar year or (ii) the transfer of
               the Company's intellectual property to AirNet Management, Inc.,
               an Ohio corporation, provided that AirNet Management, Inc. shall
               be a Guarantor hereunder and if, immediately after such
               transactions, no Default or Event of Default shall exist or shall
               have occurred and be continuing.

Clause (vi) of Section 5.2(i) is renumbered as Clause (vii) and a new Clause
(vi) is added to Section 5.2(i) as follows:

                      (vi) Indebtedness of the Company in aggregate amount not
               to exceed $100,000,000 to AirNet Management, Inc., provided that
               such Indebtedness is subordinated to all Advances and all other
               obligations pursuant to any Loan Documents and no payments,
               whether of principal, interest or otherwise are made on such
               Indebtedness until after all Advances and all other obligations
               pursuant to any Loan Documents are paid in full and all
               Commitments are terminated.

        1.3 Schedule 4.4 attached to the Credit Agreement is deleted in its
entirety and Schedule 4.4 attached to this Amendment shall be deemed substituted
in place thereof.

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ARTICLE 2.
                              CONDITIONS PRECEDENT

               This Amendment shall not become effective until each of the
following has been satisfied:

        2.1 The Subsidiary Guaranty dated of even date herewith shall be signed
by AirNet Management, Inc. (the "Subsidiary Guarantor").

        2.2 The Subordination Agreement dated of even date herewith shall be
signed by the Subsidiary Guarantor, the Company and the Agent.

        2.3 Copies of resolutions adopted by the Board of Directors of the
Subsidiary Guarantor, certified by an officer of the Subsidiary Guarantor as
being true and correct and in full force and effect without amendment as of the
date hereof, authorizing the Subsidiary Guarantor to enter into the Subsidiary
Guaranty and the Subordination Agreement and any other documents or agreements
executed pursuant thereto, if any, shall have been delivered to the Agent.

        2.4 The Agent determines that the Subordinated Revolving Credit
Agreement between the Company and the Subsidiary Guarantor and the Subordinated
Revolving Loan Promissory Note are satisfactory and the Agent approves of each
of the foregoing.

        2.5 This Amendment shall be signed by the Company and the Required
Lenders.

        2.6 Such other documents and agreements requested by the Agent.

ARTICLE 3.
                                 REPRESENTATIONS

               The Company represents and warrants to the Agent and the Lenders
that:

        3.1 The execution, delivery and performance of this Amendment are within
its powers, has been duly authorized and is not in contravention with any law,
of the terms of its Articles of Incorporation or By-laws, or any undertaking to
which it is a party or by which it is bound.

        3.2 This Amendment is the legal, valid and binding obligation of the
Company enforceable against it in accordance with the terms hereof.

        3.3 After giving effect to the amendments herein contained, the
representations and warranties contained in Article IV of the Credit Agreement
are true on and as of the date hereof with the same force and effect as if made
on and as of the date hereof.

        3.4 No Event of Default or Default exists or has occurred and is
continuing on the date hereof.

        3.5 Other than AirNet Management, Inc., there are no other Significant
Subsidiaries in existence as of the date of this Amendment.

ARTICLE 4.
                                 MISCELLANEOUS.

        4.1 This Amendment shall not become effective until the Agent determines
that the conditions precedent contained in Article 2 of this Amendment are
satisfied and this Amendment shall be signed by the Company, the Agent and the
Required Lenders.

        4.2 References in the Credit Agreement or in any Note or other Loan
Document to the Credit Agreement shall be deemed to be references to the Credit
Agreement as amended hereby and as further amended from time to time.

        4.3 Except as expressly amended hereby, the Company agrees that the
Credit Agreement, the Notes and all other documents and agreements executed by
the Company in connection with the Credit Agreement in favor of the Agent or any
Lender are ratified and confirmed and shall remain in full force and effect and
that it has no set off, counterclaim or defense with respect to any of the
foregoing. Terms used but not defined herein shall have the respective meanings
ascribed thereto in the Credit Agreement.

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        4.4 This Amendment may be signed upon any number of counterparts with
the same effect as if the signatures thereto and hereto were upon the same
instrument.

               IN WITNESS WHEREOF, the parties signing this Amendment have
caused this Amendment to be executed and delivered as of the day and year first
above written.

                              AIRNET SYSTEMS, INC.

                              By: ____________________________________

                                  Its: _______________________________

                              BANK ONE, MICHIGAN, as Agent and as a Lender

                              By: ____________________________________

                                  Its: _______________________________

                              BANK ONE, NA

                              By: ____________________________________

                                  Its: _______________________________

                              KEYBANK NATIONAL ASSOCIATION

                              By: ____________________________________

                                  Its: _______________________________

DETROIT  7-1836  488754

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                                  SCHEDULE 4.4

                                  SUBSIDIARIES

                               Float Control, Inc.
                             AirNet Management, Inc.

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