**EXHIBIT 4.21****THIRD CHANGE IN TERMS AGREEMENT**     THIS THIRD CHANGE IN TERMS AGREEMENT (this “Change in Terms”), is made and entered intoeffective as of November 10, 2005, by and between AirNet Systems, Inc., an Ohio corporation(“Borrower”) and The Huntington National Bank, a national banking association, with a bankingoffice at 41 South High Street, Columbus, Ohio 43215, in its capacity as administrative agent(“Agent”) for and on behalf of the Lenders from time to time party to the Credit Agreementdescribed below. Each capitalized term used but not otherwise defined herein shall have the meaningascribed to it in the Credit Agreement.BACKGROUND INFORMATION     A. Pursuant to the Amended and Restated Credit Agreement dated as of May 28, 2004 (asamended by the First Change in Terms and the Second Change in Terms, and as the same may befurther amended, modified, supplemented, extended, restated or replaced from time to time, the“Credit Agreement”) among Borrower, the Lenders, and the Agent, the Lenders agreed to providecertain credit facilities to the Borrower (collectively, the “Loans”).     B. Borrower and Agent entered into a certain Change in Terms Agreement dated November 12,2004, pursuant to which certain terms and provisions of the Credit Agreement were modified (the“First Change in Terms”).     C. Borrower and Agent entered into a certain Second Change in Terms Agreement dated March 24,2005, pursuant to which certain terms and provisions of the Credit Agreement were further modified(the “Second Change in Terms”).     D. Borrower, having failed to comply with the financial covenants required pursuant to Section6.24 of the Credit Agreement, has requested that Agent waive the Default existing under the CreditAgreement as a result of Borrower’s failure to maintain such financial covenants, and acting uponthe authority of the Required Lenders, Agent has agreed to do so on certain conditions, includingwithout limitation, that Borrower enter into this Change in Terms.AGREEMENT     NOW THEREFORE, in consideration of the mutual covenants and agreements contained herein, Agentand Borrower hereby agree as follows:     1. *Change in Terms*. The Credit Agreement, and, to the extent applicable, the other LoanDocuments, are hereby modified to provide as follows:     (i) The definition of “Consolidated EBIT,” as set forth in Section 1.1 of theCredit Agreement, is hereby revised and replaced in its entirety by the following:“*Consolidated EBIT*” means, with respect to any period, ConsolidatedNet Income *plus*, (a) to the extent deducted from revenues in determiningConsolidated Net Income, (i) Consolidated Interest Expense, (ii) income taxexpense, calculated for the Borrower and its Subsidiaries on a consolidatedbasis, and (iii) extraordinary losses (determined in accordance withAgreement Accounting Principles) incurred other than in the ordinary courseof business, calculated for the Borrower and its Subsidiaries on aconsolidated basis, *plus*(b) for the fiscal quarter ending September 30,2005 only, an amount equal to $16,073,000.00 (which reflects the non-cashimpairment charge recognized by Borrower in the fiscal quarter endingSeptember 30, 2005), *minus,*to the extent included in Consolidated NetIncome, extraordinary gains (determined in accordance with AgreementAccounting Principles) realized other than in the ordinary course ofbusiness, calculated for the Borrower and its Subsidiaries on a consolidatedbasis.
 

 
     (ii) The definition of “Consolidated EBITDA,” as set forth in Section 1.1 ofthe Credit Agreement, is hereby revised and replaced in its entirety by the following:“*Consolidated EBITDA*” means with respect to any period, ConsolidatedNet Income *plus*, (a) to the extent deducted from revenues in determiningConsolidated Net Income, (i) Consolidated Interest Expense, (ii) income taxexpense, calculated for the Borrower and its Subsidiaries on a consolidatedbasis, (iii) depreciation, calculated for the Borrower and its Subsidiarieson a consolidated basis, (iv) amortization, calculated for the Borrower andits Subsidiaries on a consolidated basis; and (v) extraordinary losses(determined in accordance with Agreement Accounting Principles) incurredother than in the ordinary course of business, calculated for the Borrowerand its Subsidiaries on a consolidated basis, *plus*(b) for the fiscalquarter ending September 30, 2005 only, an amount equal to $16,073,000.00(which reflects the non-cash impairment charge recognized by Borrower in thefiscal quarter ending September 30, 2005), *minus,*to the extent included inConsolidated Net Income, extraordinary gains (determined in accordance withAgreement Accounting Principles) realized other than in the ordinary courseof business, calculated for the Borrower and its Subsidiaries on aconsolidated basis.     2. Truth of Representations and Warranties; No Defaults. Borrower hereby representsand warrants that the following are true and correct as of the date of this Change in Terms:     (a) After giving effect to that certain letter agreement dated of even date herewith byand among Borrower (herein, the “Waiver”), the Guarantors and Agent and the waiver providedtherein, the representations and warranties of Borrower and the Guarantors contained in theLoan Documents to which each is a party are true and correct on and as of the date of thisChange in Terms as if made on and as of such date, unless stated to relate to a specificearlier date;     (b) No event or condition exists which constitutes a breach, Default or UnmaturedDefault under the Loan Documents;     (c) All financial information heretofore provided to Agent and/or the Lenders inconnection with the indebtedness made pursuant to the Loan Documents is true, accurate andcomplete in all material respects;     (d) Neither this Change in Terms nor any other document, certificate or writtenstatement furnished to Agent and/or the Lenders in connection with the indebtednessevidenced and secured by the Loan Documents contains any untrue statement of a material factor omits to state a material fact necessary in order to make the statements contained hereinand therein not misleading;     (e) Borrower and the Guarantors have full power and authority (i) to execute, deliverand perform, or to acknowledge and agree to the terms and provisions of, this Change inTerms, as applicable, and (ii) to incur the obligations provided for herein, all of whichhave been duly authorized by all necessary and proper corporate or limited liability companyaction, as applicable;     (f) No consent, waiver or authorization of, or filing with, any person or anygovernmental authority is required to be made or obtained by Borrower or the Guarantors inconnection with the borrowings under the Loan Documents, or the execution, delivery,performance, validity or enforceability of this Change in Terms;     (g) This Change in Terms and the Loan Documents constitute the legal, valid and bindingobligation of Borrower and the Guarantors enforceable against them in accordance with theterms hereof and thereof, as applicable; and     (h) The execution and delivery by Borrower and the Guarantors of this Change in Termsand the performance by Borrower and the Guarantors of the Loan Documents to which each is aparty, as modified by this Change in Terms and by the Waiver: (i) do not and will notviolate any law or regulation; (ii) do not and will not violate any order, decree orjudgment by which Borrower or the Guarantors, as applicable, are bound; (iii) do not and will not violate or conflict with, result in abreach of or constitute (with notice, lapse of time, or otherwise) a default under anymaterial agreement, mortgage, indenture or other contractual obligation to which Borrower orany of the Guarantors is a party, or by which Borrower’s or any of
 

 
the Guarantors’properties are bound; and (iv) do not and will not result in the creation or imposition ofany lien upon any property or assets of Borrower or any of the Guarantors.     3. Ratification of Loan Documents. This Change in Terms constitutes only amodification of the Credit Agreement and the other Loan Documents and Borrower hereby acknowledges,ratifies and confirms all of the provisions thereof, except as herein expressly modified, includingprovision for the acceleration of the maturity of the Loans, and for the enforcement by Agentand/or the Lenders of all remedies any of them may have according to law. In addition, Borroweracknowledges, ratifies and confirms any and all security interests previously granted in connectionwith the Loans as continuing in full force and effect.     4. No Course of Dealing; Waiver. Borrower expressly acknowledges and agrees that theexecution of this Change in Terms shall not constitute a waiver of, and shall not preclude theexercise of, any right, power or remedy granted to Agent and/or the Lenders in the Loan Documents,or as provided by law, except to the extent expressly provided herein. No previous modification,extension or compromise entered into with respect to any indebtedness of Borrower to Agent and/orthe Lenders shall constitute a course of dealing or be inferred or construed as constituting anexpress or implied understanding to enter into any future modification, extension or compromise,whether or not the same was in writing. No past, present or future delay on the part of Agentand/or any Lender in exercising any right, power or remedy shall operate as a waiver thereof, orotherwise prejudice Agent’s or any Lender’s rights, powers or remedies.     5. Promise to Pay. Borrower hereby covenants and promises to pay to the order ofAgent, the unpaid principal balance of the Loans, together with interest as provided in the CreditAgreement and the other Loan Documents, and hereby promises to perform all of the covenants,conditions, stipulations and agreements as contained in the Loan Documents and in any otherdocument or instrument executed in connection therewith or referencing the same (as modified bythis Change in Terms).     6. Setoffs, Claims and Defenses. Borrower hereby certifies that, as of the datehereof, it has no setoffs, counter-claims or other defenses of any nature whatsoever to the paymentof any part of the obligations owed to Agent and/or any Lender as of the date of execution of thisChange in Terms.     7. Governing Law. This Change in Terms shall be interpreted and construed inaccordance with and governed by the laws of the State of Ohio (without respect to conflict of lawprinciples). Further, the parties hereto intend that this Change in Terms shall be in compliancewith all applicable laws and shall be enforceable in accordance with its terms. If any provisionof this Change in Terms shall be illegal or unenforceable with respect to the Loan Documents, suchprovision shall be deemed cancelled to the extent necessary, but the remaining provisions shall notbe affected hereby.     8. Further Assurances. Borrower and the Guarantors further agree to execute anddeliver any and all further documents and to take any and all other steps or actions reasonablydeemed necessary by Agent to effectuate this Change in Terms.     9. Affirmation of Other Obligors. Upon the request of Agent, Borrower shall obtainthe acknowledgment and acceptance by each other party obligated in any way with respect to theLoans or otherwise in connection with the credit extended pursuant to the Credit Agreement,including, without limitation, the Guarantors and any other guarantor, co-borrower, pledgor orother accommodation party or party granting collateral security for the Loans and other obligationsunder the Loan Documents and otherwise, that the obligations and agreements of each such party tothe Lenders and/or the Agent under the Loan Documents, as applicable, or otherwise, shall continuein full force and effect with respect to the indebtedness evidenced and secured by the LoanDocuments, irrespective of any modification made in this Change in Terms, which acknowledgement andacceptance shall be in a writing executed by each such party and satisfactory to Agent.     10. Acknowledgment by Lenders. This Change in Terms shall only be effective upon theacknowledgment, consent and acceptance by the Required Lenders, which acknowledgement, consent andacceptance shall be evidenced by execution of this Change in Terms by Lenders constituting theRequired Lenders.
 

 
     11. Successors and Assigns. This Change in Terms shall be binding upon the partieshereto and their respective successors and assigns, and shall inure to the benefit of Agent and itssuccessors and assigns.     12. Costs and Expenses. Borrower also agrees to reimburse Agent for all costs andexpenses incurred in the preparation, execution and delivery of this Change in Terms, includingreasonable attorneys’ fees.     13. Titles and Headings. The titles and headings herein are intended to promoteconvenience and are not a part of this Change in Terms for purposes of interpreting and applyingthe provisions hereof.     14. Counterparts. This Change in Terms may be executed in any number of counterparts,all of which taken together shall constitute one agreement, and any of the parties hereto mayexecute this Change in Terms by signing any such counterpart. This Change in Terms shall beeffective when it has been executed by Borrower, Agent, the Required Lenders and the Guarantors.     15. WAIVER OF JURY TRIAL. BORROWER AND AGENT HEREBY WAIVE TRIAL BY JURY IN ANYJUDICIAL PROCEEDING INVOLVING, DIRECTLY OR INDIRECTLY, ANY MATTER (WHETHER SOUNDING IN TORT,CONTRACT OR OTHERWISE) IN ANY WAY ARISING OUT OF, RELATED TO, OR CONNECTED WITH THIS CHANGE INTERMS OR ANY OF THE LOAN DOCUMENTS OR THE RELATIONSHIP ESTABLISHED HEREUNDER OR THEREUNDER.     16. Confession of Judgment. Borrower hereby irrevocably authorizes anyattorney-at-law, including any attorney-at-law employed or retained by Agent to appear for it inany action on this Change in Terms or any of the Loan Documents at any time after the same becomesdue as herein or therein provided in any court of record situated in the county where this warrantwas signed (being Franklin County, Ohio), or in the county where Borrower then resides or can befound, to waive the issuing and service of process, and confess a judgment in favor of the holderof this Change in Terms and any such Loan Documents against Borrower, for the amount that may thenbe due, with interest at the rate(s) provided for herein, together with the costs of suit, and towaive and release all errors in said proceedings and the right to appeal from the judgmentrendered. Borrower consents to the jurisdiction and venue of such court. Borrower waives anyconflict of interest that any attorney-at-law employed or retained by Agent may have in confessingjudgment hereunder and consents to the payment of a legal fee to any attorney-at-law confessingjudgment hereunder.     IN WITNESS WHEREOF, Borrower and Agent have caused this Change in Terms to be executedeffective as of the day and year first above written.BORROWER: