<PAGE>   1
                                                             Exhibit 10.30

      THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF PHOENIX, ARIZONA



                                       TO



                           NORWEST BANK ARIZONA, N.A.
                                     Trustee



                        --------------------------------



                               INDENTURE OF TRUST


                        --------------------------------


                                    SECURING
                                   $29,300,000
      THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF PHOENIX, ARIZONA
                       AIRPORT FACILITIES REFUNDING BONDS
                      (AMERICA WEST AIRLINES, INC. PROJECT)
                                   SERIES 1998


                        --------------------------------



                            Dated as of April 1, 1998
<PAGE>   2
                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                                              Page
<S>                                                                                                                           <C>
Recitals.........................................................................................................................1
Form of Face of Bond.............................................................................................................3
Form of Trustee's Certificate of Authentication..................................................................................5
Form of Reverse of Bond..........................................................................................................5
Form of Assignment...............................................................................................................8
Granting Clauses.................................................................................................................9

ARTICLE I                  DEFINITIONS..........................................................................................11

       Section 1.01.           Definitions......................................................................................11

ARTICLE II                 THE BONDS............................................................................................16

       Section 2.01.           Authorized Amount and Purpose of Bonds...........................................................16
       Section 2.02.           Issuance of Bonds................................................................................16
       Section 2.03.           Ownership, Transfer, Exchange and Registration of Bonds..........................................17
       Section 2.04.           Execution; Limited Obligation....................................................................18
       Section 2.05.           Authentication...................................................................................18
       Section 2.06.           Mutilated, Destroyed, Lost or Stolen Bonds.......................................................18
       Section 2.07.           Cancellation and Destruction of Surrendered Bonds................................................19
       Section 2.08.           Delivery of the Bonds............................................................................19
       Section 2.09.           Book Entry System................................................................................20

ARTICLE III                REDEMPTION OF BONDS BEFORE MATURITY..................................................................20

       Section 3.01.           Optional Redemption..............................................................................20
       Section 3.02.           Reserved.........................................................................................21
       Section 3.03.           Mandatory Redemption.............................................................................21
       Section 3.04.           Notice of Redemption.............................................................................21
       Section 3.05.           Deposit of Funds.................................................................................23
       Section 3.06.           Partial Redemption of Bonds......................................................................23
       Section 3.07.           Selection Of Bonds For Redemption................................................................23

ARTICLE IV                 PAYMENT; FURTHER ASSURANCES..........................................................................24

       Section 4.01.           Payment of Principal or Redemption Price of and Interest on Bonds................................24
       Section 4.02.           Performance of Covenants; The Issuer.............................................................24
       Section 4.03.           Right to Payments Under Agreement; Instruments of Further Assurance..............................24
       Section 4.04.           Financing Statements.............................................................................25
       Section 4.05.           Inspection of Project Books......................................................................25
       Section 4.06.           Rights under Agreement...........................................................................25
</TABLE>

                                      -i-
<PAGE>   3
<TABLE>
<CAPTION>
<S>                                                                                                                            <C>
ARTICLE V                  REVENUES AND FUNDS...................................................................................26

       Section 5.01.           Source of Payment of Bonds.......................................................................26
       Section 5.02.           Creation of the Bond Fund........................................................................26
       Section 5.03.           Payments into the Bond Fund......................................................................26
       Section 5.04.           Use of Moneys in the Bond Fund...................................................................26
       Section 5.05.           Custody of the Bond Fund.........................................................................26
       Section 5.06.           Non-Presentment of Bonds.........................................................................27
       Section 5.07.           Trustee's Fees, Charges and Expenses.............................................................27
       Section 5.08.           Moneys To Be Held in Trust.......................................................................27
       Section 5.09.           Repayment to the Company from the Bond Fund......................................................27
       Section 5.10.           Revenues To Be Paid Over to Trustee..............................................................27
       Section 5.11.           Payments of Principal and Interest...............................................................28
       Section 5.12.           Revenues To Be Held for All Bondholders; Certain Exceptions......................................28
       Section 5.13.           Tax Agreement....................................................................................28
       Section 5.14.           Cost of Issuance Fund............................................................................28

ARTICLE VI                 INVESTMENT OF MONEYS.................................................................................28

       Section 6.01.           Investment of Bond Fund Moneys...................................................................28
       Section 6.02.           Investments; Arbitrage...........................................................................28

ARTICLE VII                DEFEASANCE...........................................................................................29

       Section 7.01.           Defeasance.......................................................................................29

ARTICLE VIII               DEFAULT PROVISIONS; REMEDIES.........................................................................30

       Section 8.01.           Defaults; Events of Default......................................................................30
       Section 8.02.           Acceleration.....................................................................................31
       Section 8.03.           Remedies; Rights Of Bondholders..................................................................31
       Section 8.04.           Right of Bondholders to Direct Proceedings.......................................................32
       Section 8.05.           Application of Moneys............................................................................32
       Section 8.06.           Remedies Vested in Trustee.......................................................................32
       Section 8.07.           Rights and Remedies of Bondholders...............................................................33
       Section 8.08.           Termination of Proceedings.......................................................................33
       Section 8.09.           Waivers of Events of Default.....................................................................33
       Section 8.10.           Opportunity of Company to Cure Events of Default.................................................34

ARTICLE IX                 THE TRUSTEE..........................................................................................35

       Section 9.01.           Acceptance of the Trusts.........................................................................35
       Section 9.02.           Corporate Trustee Required; Eligibility..........................................................38
       Section 9.03.           Fees, Charges and Expenses of Trustee............................................................38
       Section 9.04.           Notice to Bondholders If Default Occurs..........................................................39
       Section 9.05.           Intervention by Trustee..........................................................................39
       Section 9.06.           Successor Trustee................................................................................39
</TABLE>

                                      -ii-
<PAGE>   4
<TABLE>
<CAPTION>
<S>                                                                                                                             <C>
       Section 9.07.           Resignation by the Trustee.......................................................................39
       Section 9.08.           Removal of the Trustee...........................................................................40
       Section 9.09.           Appointment of Successor Trustee.................................................................40
       Section 9.10.           Concerning Any Successor Trustees................................................................40
       Section 9.11.           Appointment of Co-Trustee........................................................................41

ARTICLE X                  SUPPLEMENTAL INDENTURES..............................................................................42

       Section 10.01.          Supplemental Indentures Not Requiring Consent of Bondholders.....................................42
       Section 10.02.          Supplemental Indentures Requiring Consent of Bondholders.........................................43
       Section 10.03.          Consents to Supplemental Indentures..............................................................44
       Section 10.04.          Reliance on Opinions of Counsel..................................................................44

ARTICLE XI                 AMENDMENT OF AGREEMENT...............................................................................44

       Section 11.01.          Amendments, Etc., to Agreement Not Requiring Consent of Bondholders..............................44
       Section 11.02.          Amendments, Etc., to Agreement Requiring Consent of Bondholders..................................45
       Section 11.03.          Reliance on Opinions of Counsel..................................................................45

ARTICLE XII                MISCELLANEOUS........................................................................................46

       Section 12.01.          Consents, Etc., Of Bondholders...................................................................46
       Section 12.02.          Limitation of Rights.............................................................................46
       Section 12.03.          Severability.....................................................................................46
       Section 12.04.          Notices..........................................................................................46
       Section 12.05.          Holidays.........................................................................................47
       Section 12.06.          Counterparts.....................................................................................47
       Section 12.07.          Applicable Law...................................................................................47
       Section 12.08.          Captions.........................................................................................47
       Section 12.09.          Notice Regarding Cancellation of Contracts.......................................................47

Signature Page..................................................................................................................48


EXHIBIT I                  FORM OF INVESTOR LETTER
</TABLE>

                                      -iii-
<PAGE>   5
         THIS INDENTURE OF TRUST, made and entered into as of April 1, 1998, by
and between THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF PHOENIX,
ARIZONA, an Arizona nonprofit corporation and political subdivision of the State
of Arizona (the "Issuer"), and NORWEST BANK ARIZONA, N.A., as Trustee (the
"Trustee"), a banking corporation duly organized, existing and authorized to
accept and execute trusts of the character herein set out under the laws of the
State of Arizona, with its principal corporate trust office located in Phoenix,
Arizona;

                                   WITNESSETH:

         WHEREAS, the Issuer is authorized and empowered under Title 35, Chapter
5, Arizona Revised Statutes, as amended (the "Act"), to issue revenue bonds in
accordance with Article 2 of the Act and to make secured or unsecured loans for
the purpose of financing or refinancing costs of certain airport facilities, to
charge and collect interest on such loans and pledge the proceeds of loan
agreements as security for the payment of principal of and interest on bonds, or
designated issues of bonds, issued by the Issuer and any agreements in
connection therewith, whenever the board of directors finds such loans to be in
furtherance of the purposes of the Issuer; and

         WHEREAS, the Issuer has heretofore issued and sold its Variable Rate
Airport Facility Revenue Bonds (America West Airlines, Inc. Project) Series 1986
in the original aggregate principal amount of $54,000,000, of which $29,300,000
is currently outstanding (the "Prior Bonds"), pursuant to an Indenture of Trust,
dated as of August 1, 1986 (the "Prior Indenture"), between the Issuer and
Norwest Bank Arizona, N.A., as successor trustee, and has loaned the proceeds
thereof to America West Airlines, Inc., a Delaware corporation (the "Company"),
for the purpose of financing the airport facilities more particularly described
in the Prior Indenture (the "Project").

         WHEREAS, the Company has requested that the Issuer issue and sell bonds
to refund the Prior Bonds and refinance the Project; and

         WHEREAS, pursuant to the Act, the Issuer has determined to issue and
sell its airport facility refunding bonds as provided herein (the "Bonds") and
to lend the proceeds thereof to the Company pursuant to the Financing Agreement
of even date herewith (the "Agreement"), between the Issuer and the Company, for
the purpose of refunding the Prior Bonds; and

         WHEREAS, the issuance and sale of the Bonds and the loan of the
proceeds thereof to the Company to refund the Prior Bonds will serve the
purposes of the Issuer and the Act and in all respects conform to the provisions
and requirements of the Act; and

         WHEREAS, in order to provide for the authentication and delivery of the
Bonds, to establish and declare the terms and conditions upon which the Bonds
are to be issued and secured and to secure the payment of the principal thereof
and of the interest and premium, if any, thereon, the Issuer has authorized the
execution and delivery of this Indenture, and
<PAGE>   6
         WHEREAS, all Bonds issued under this Indenture will be secured by a
pledge and assignment of the Issuer's rights under the aforesaid Agreement; and

         WHEREAS, the Bonds and the Trustee's certificate of authentication and
the form of assignment to be endorsed thereon are all to be in substantially the
following forms, with necessary and appropriate variations, omissions and
insertions as permitted or required by this Indenture, to wit:

                                      -2-
<PAGE>   7
                             [FORM OF FACE OF BOND]

                            UNITED STATES OF AMERICA

      THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF PHOENIX, ARIZONA

                        AIRPORT FACILITIES REFUNDING BOND
                      (AMERICA WEST AIRLINES, INC. PROJECT)
                                   SERIES 1998

Registered                                                           Registered

No. R-                                                              $29,300,000

Interest Rate:      Dated Date:        Maturity Date:                  CUSIP:

6.30%               April 1, 1998      April 1, 2023

Registered Owner: Cede & Co.

Principal Amount: Twenty-nine million three hundred thousand             Dollars

           [1] THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF PHOENIX,
ARIZONA (the "Issuer"), an Arizona nonprofit corporation and political
subdivision of the State of Arizona, for value received, hereby promises to pay
(but in each case only out of the source hereinafter provided) to the Registered
Owner identified above, or registered assigns as hereinafter provided, on the
Maturity Date identified above, the Principal Amount identified above, and to
pay interest on said Principal Amount until payment of said Principal Amount has
been made or duly provided for at the Interest Rate identified above, on April 1
and October 1 of each year, commencing on October 1, 1998, and to pay interest
on overdue principal and, to the extent permitted by law, on overdue interest at
the rate borne by this Bond, except as the provisions hereinafter set forth with
respect to redemption prior to maturity may become applicable hereto, the
principal of, premium, if any, and interest on this Bond being payable in lawful
money of the United States of America at the designated Corporate Trust Office
of Norwest Bank Arizona, N.A., as Trustee, or its successor in trust (the
"Trustee"); provided, however, payment of interest on any Interest Payment Date
shall be made to the Owner hereof as of the close of business on the Record Date
with respect to such Interest Payment Date and shall be (i) paid by check or
draft mailed on such Interest Payment Date to such Owner hereof at his address
as it appears on the registration books of the Issuer maintained by the Trustee
or at such other address as is furnished in writing by such Owner to the Trustee
as Bond Registrar not later than the close of business on the Record Date or
(ii) transmitted by wire transfer to an account with a commercial bank located
within the United States of America if such Owner owns at least

                                      -3-
<PAGE>   8
$1,000,000 in aggregate principal amount of the Bonds and shall have provided
wire transfer instructions to the Trustee prior to the close of business on such
Record Date.

                        --------------------------------

         REFERENCE IS HEREBY MADE TO THE FURTHER PROVISIONS OF THIS BOND SET
FORTH ON THE REVERSE HEREOF AND SUCH FURTHER PROVISIONS SHALL FOR ALL PURPOSES
HAVE THE SAME EFFECT AS IF SET FORTH AT THIS PLACE.

                        --------------------------------

          [16] THIS BOND DOES NOT, AND SHALL NEVER, CONSTITUTE AN INDEBTEDNESS
OF THE CITY OF PHOENIX, THE STATE OF ARIZONA OR THE ISSUER WITHIN THE MEANING OF
ANY STATE CONSTITUTIONAL PROVISION OR STATUTORY LIMITATION, AND THIS BOND SHALL
NEVER CONSTITUTE OR GIVE RISE TO A PECUNIARY LIABILITY OF SAID CITY, SAID STATE
OR THE ISSUER OR A CHARGE AGAINST THE GENERAL CREDIT OR TAXING POWERS OF SAID
CITY OR SAID STATE OR A CHARGE AGAINST THE GENERAL CREDIT OF THE ISSUER. THE
ISSUER HAS NO TAXING POWER.

          [17] IT IS HEREBY CERTIFIED, RECITED AND DECLARED that all acts and
conditions required to be performed precedent to and in the execution and
delivery of the Indenture and the issuance of this Bond have been performed in
due time, form and manner as required by law, and that the issuance of this Bond
and the issue of which it forms a part does not exceed or violate any
constitutional or statutory limitation.

          [18] This Bond shall not be valid or become obligatory for any purpose
or be entitled to any security or benefit under the Indenture unless and until
the certificate of authentication hereon shall have been duly executed by the
Trustee.

          [19] IN WITNESS WHEREOF, THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE
CITY OF PHOENIX, ARIZONA has caused this Bond to be executed in its name by the
manual or facsimile signature of its President and attested by the manual or
facsimile signature of its Secretary, all as of April 1, 1998.


                                 THE INDUSTRIAL DEVELOPMENT AUTHORITY
                                   OF THE CITY OF PHOENIX, ARIZONA


                                 By
                                   --------------------------------------------
                                    President

Attest:



--------------------------------
Secretary

                                      -4-
<PAGE>   9
                [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

         This Bond is one of the Bonds described in the within-mentioned
Indenture of Trust.

Date of Authentication:                  _____________________________________,
                                         as Trustee


                                         By
________________________________         ______________________________________
                                            Authorized Signatory

                            [FORM OF REVERSE OF BOND]

           [2] This Bond is one of an authorized issue of bonds limited in
aggregate principal amount to $29,300,000 (the "Bonds") issued pursuant to a
resolution duly adopted by the governing body of the Issuer on March 19, 1998
(the "Resolution"), and the applicable provisions of Title 35, Chapter 5,
Arizona Revised Statutes, as supplemented and amended to the date hereof (the
"Act"), and issued under an Indenture of Trust (the "Indenture") dated as of
April 1, 1998, between the Issuer and the Trustee, for the purpose of refunding
bonds of the Issuer the proceeds of which were used to finance costs of certain
airport facilities located within the boundaries of the Issuer (the "Project")
for America West Airlines, Inc. (the "Company"). Proceeds from the sale of the
Bonds are to be loaned by the Issuer to the Company under the terms of a
Financing Agreement, dated as of April 1, 1998 (the "Agreement"), between the
Issuer and the Company, which provides for the repayment of such loan by the
Company.

           [3] The Bonds are all issued under and equally and ratably secured by
and entitled to the benefits of the Indenture (except as otherwise expressly set
forth in the Indenture), including the security of a pledge and assignment of
certain revenues and receipts derived by the Issuer pursuant to the Agreement,
and all receipts of the Trustee credited under the provisions of the Indenture
against such payments, and from any other moneys held by the Trustee under the
Indenture for such purpose, and there shall be no other recourse against the
Issuer or any property now or hereafter owned by it.

           [4] The Bonds are issuable as registered Bonds without coupons in
Authorized Denominations. Subject to the limitations, upon payment of the
charges provided in the Indenture and upon surrender and cancellation hereof,
this Bond may be exchanged for a like aggregate principal amount of Bonds of
other Authorized Denominations. This Bond is transferable by the Owner hereof in
person or by his attorney duly authorized in writing at the designated Corporate
Trust Office of the Trustee but only in the manner, subject to the limitations
and upon payment of the charges provided in the Indenture, and upon surrender
and cancellation of this Bond. Upon such transfer a new registered Bond or
Bonds, of Authorized Denomination or Authorized Denominations, for the same
aggregate principal amount, will be issued to the transferee in exchange
herefor.

                                      -5-
<PAGE>   10
           [5] The Bonds are subject to redemption prior to maturity, at the
option of the Company, on or after April 1, 2008, in whole or in part on the
dates set forth below, at the redemption prices (expressed as percentages of
principal amount) set forth in the following table plus accrued interest, if
any, to the redemption date:


<TABLE>
<CAPTION>
                               Redemption Dates                                                  Redemption Prices
                               ----------------                                                  -----------------
<S>               <C>                                                                            <C>
                  April 1, 2008 and October 1, 2008                                                      102%

                  April 1, 2009 and October 1, 2009                                                      101%

                  April 1, 2010 and any Interest Payment Date thereafter                                 100%
</TABLE>

           [6] The Bonds shall be redeemed at 100% of the principal amount
thereof plus accrued interest, if any, to the redemption date within 180 days
after (i) receipt by the Company of written notice of the issuance of a private
letter ruling or a technical advice memorandum by the Internal Revenue Service
in a proceeding in connection with which the Company has had the opportunity to
participate or (ii) the Company receives written notice of a final determination
by any court of competent jurisdiction of the United States in a proceeding to
which the Company is a party or in which the Company has had the opportunity to
participate, in either case, to the effect that, as a result of a failure by the
Company to observe any covenant, agreement, representation or warranty in the
Agreement or the Project Certificate, the interest payable on the Bonds is
included in the gross income for federal income tax purposes of the Owners or
beneficial owners thereof (other than a person who is a "substantial user" of
the Project or a "related person" within the meaning of Section 147(a) of the
Code or Section 103(b)(13) of the 1954 Code). Upon the occurrence of any such
event, the Bonds shall be redeemed in whole unless, in the opinion of Bond
Counsel, the redemption of a portion of the Outstanding Bonds would have the
result that interest payable on the Bonds remaining Outstanding after such
redemption would not be included in the gross income for federal income tax
purposes of any Owners or beneficial owners of the Bonds (other than a person
who is a "substantial user" of the Project or a "related person" within the
meaning of Section 147(a) of the Code or Section 103(b)(13) of the 1954 Code),
in which event only such portion of the Outstanding Bonds shall be redeemed.

           [7] In the event any of the Bonds or Authorized Denominations thereof
are called for redemption, notice thereof identifying the Bonds or portions
thereof to be redeemed will be given by the Trustee upon mailing a copy of the
redemption notice by first class mail at least thirty days prior to the date
fixed for redemption to the Owner of each Bond to be redeemed in whole or in
part at the address shown on the registration books; provided, however, that
failure to give such notice by mailing, or any defect therein, shall not affect
the validity of the proceedings for the redemption of any Bond or portion
thereof with respect to which no such failure occurred. All Bonds so called for
redemption will cease to bear interest after the specified redemption date
provided funds for their redemption are on deposit at the place of payment at
that time. In the event any Bond is called for redemption

                                      -6-
<PAGE>   11
in part only, the Issuer shall execute and the Trustee shall authenticate and
deliver to the Owner thereof a new Bond or new Bonds of Authorized Denominations
in aggregate principal amount equal to the unredeemed portion of the Bond
surrendered. Additional notice of redemption of Bonds or portions thereof may be
given by the Trustee as provided in the Indenture, including notice to certain
services and by publication, but no failure to give any such additional notice
or any defect therein shall defeat the effectiveness of a call for redemption if
notice thereof is given as above prescribed.

           [8] With respect to any notice of optional redemption of Bonds,
unless upon the giving of such notice such Bonds shall be deemed to have been
paid within the meaning of Article VII of the Indenture, such notice may state
(if so directed by the Company in writing) that such redemption shall be
conditional upon the receipt by the Trustee on or prior to the date fixed for
such redemption of moneys sufficient to pay the principal of, and premium, if
any, and interest on, such Bonds to be redeemed, and that if such moneys shall
not have been so received said notice shall be of no force and effect and the
Issuer shall not be required to redeem such Bonds. In the event that such notice
of redemption contains such a condition and such moneys are not so received, the
redemption shall not be made and the Trustee shall within a reasonable time
thereafter give notice, in the manner in which the notice of redemption was
given, that such moneys were not so received.

           [9] This Bond and all other Bonds of the series of which it forms a
part are issued pursuant to and in full compliance with the Constitution and
laws of the State of Arizona, particularly the Act, and pursuant to further
proceedings adopted by the governing authority of the Issuer, which proceedings
authorize the execution and delivery of the Indenture. This Bond and the series
of which it forms a part are special limited obligations of the Issuer payable
solely from the sources described herein. The Project is not security for the
Bonds.

          [10] No recourse shall be had for the payment of the principal of, or
premium, if any, or interest on, any of the Bonds or for any claim based thereon
or upon any obligation, covenant or agreement in the Indenture contained,
against any past, present or future member, director, officer, employee or agent
of the Issuer, or through the Issuer, or any successor to the Issuer, under any
rule of law or equity, statute or constitution or by the enforcement of any
assessment or penalty or otherwise, and all such liability of any such member,
director, officer, employee or agent as such is hereby expressly waived and
released as a condition of and in consideration for the execution of the
Indenture and the issuance of any of the Bonds.

          [11] The Owner of this Bond shall have no right to enforce the
provisions of the Indenture or to institute action to enforce the covenants
therein, or to take any action with respect to any event of default under the
Indenture, or to institute, appear in or defend any suit or other proceedings
with respect thereto, except as provided in the Indenture. If an Event of
Default as defined in the Indenture occurs and is continuing, the principal of
all Bonds then outstanding may be declared due and payable upon the conditions
and in the manner and with the effect provided in the Indenture.

                                      -7-
<PAGE>   12
          [12] The Issuer, the Trustee and any agent of the Issuer or the
Trustee may treat the person in whose name this Bond is registered as the Owner
hereof for the purpose of receiving payment as herein provided and for all other
purposes, whether or not this Bond be overdue, and neither the Issuer, the
Trustee nor any such agent shall be affected by notice to the contrary.

          [13] The Indenture prescribes the manner in which it may be discharged
and after which the Bonds shall no longer be secured by or entitled to the
benefits of the Indenture, except for the purposes of registration and exchange
of Bonds and of such payment, including a provision that under certain
circumstances the Bonds shall be deemed to be paid if Government Obligations
maturing as to principal and interest in such amounts and at such times as to
insure the availability of sufficient moneys to pay the principal of, and
premium, if any, and interest on, the Bonds and all necessary and proper fees,
compensation and expenses of the Trustee shall have been deposited with the
Trustee.

          [14] Modifications or alterations of the Indenture, or of any
supplements thereto, may be made only to the extent and in the circumstances
permitted by the Indenture.

          [15] Terms which are used herein as defined terms and which are not
otherwise defined herein shall have the meanings attributed to them in the
Indenture.

                              [FORM OF ASSIGNMENT]

         The following abbreviations, when used in the inscription on the face
of this Bond, shall be construed as though they were written out in full
according to applicable laws or regulations:


                               UNIF GIFT MIN ACT--

<TABLE>
<CAPTION>
<S>               <C>                                                   <C>
TEN COM           --  as tenants in common                              ____________ Custodian ___________
TEN ENT           --  as tenants by the entireties                          (Cust)               (Minor)
JT TEN            --  as joint tenants with right                       under Uniform Gifts to Minors Act
                      of survivorship and not                           ________________________________
                      as tenants in common                                                       State
</TABLE>


         Additional abbreviations may also be used though not in the above list.

         FOR VALUE RECEIVED, the undersigned sells, assigns and transfers unto

---------------------------------------------------------------------------
                         (Name and Address of Assignee)

the within Bond of The Industrial Development Authority of the City of Phoenix,
Arizona and does hereby irrevocably constitute and appoint __________________ to
transfer the said

                                      -8-
<PAGE>   13
Bond on the books kept for registration thereof with full power of substitution
in the premises.

Dated:_________________

Signature Guaranteed:

_______________________

NOTICE: The signature to this assignment must correspond with the name as it
appears upon the face of the within Bond in every particular, without alteration
or enlargement or any change whatever.

NOTICE: Signature(s) must be guaranteed by a member firm of the New York Stock
Exchange or a commercial bank or trust company.

                               [END OF BOND FORM]

         WHEREAS, the execution and delivery of the Bonds and of this Indenture
have been duly authorized and all things necessary to make the Bonds, when
executed by the Issuer and authenticated by the Trustee, valid and binding legal
obligations of the Issuer and to make this Indenture a valid and binding
agreement have been done;

               NOW, THEREFORE, THIS INDENTURE OF TRUST WITNESSETH:

         That the Issuer in consideration of the premises, the acceptance by the
Trustee of the trusts hereby created, the purchase and acceptance of the Bonds
by the purchasers thereof, one dollar duly paid to the Issuer by the Trustee at
or before the execution and delivery of these presents and of other good and
valuable considerations, the receipt of which is hereby acknowledged, and in
order to secure the payment of the principal of, and premium, if any, and
interest on, all Bonds outstanding hereunder from time to time, according to
their tenor and effect, and to secure the observance and performance by the
Issuer of all the covenants expressed or implied herein and in the Bonds, does
hereby pledge and assign unto the Trustee, and unto its successors and assigns
forever;

                              GRANTING CLAUSE FIRST

         The Agreement, including all extensions and renewals of the term
thereof, if any, together with all right, title and interest of the Issuer
therein (except for the right of the Issuer to the payment of costs, expenses,
indemnification and counsel fees pursuant to Sections 4.2(d), 4.2(e), 5.3 and
6.4 of the Agreement and any rights of the Issuer to receive any notices,
certificates, requests, requisition or other communications under the Agreement)
including, but without limiting the generality of the foregoing, the present and
continuing right to receive, receipt for, collect or make claim for any of the
moneys, income, revenues, issues, profits and other amounts payable or
receivable thereunder,

                                      -9-
<PAGE>   14
including payments made by the Company, whether payable under the Agreement or
otherwise, to bring actions and proceedings thereunder or for the enforcement
thereof, and to do any and all things which the Issuer or any other person is or
may become entitled to do under the Agreement;

                             GRANTING CLAUSE SECOND

         All payments to be received by the Issuer (except as provided in the
preceding paragraph) under the Agreement, together with all other Revenues, and
all moneys and earnings thereon held by the Trustee in the Bond Fund under the
terms of the Indenture; and

                              GRANTING CLAUSE THIRD

         Any and all other property of each name and nature from time to time
hereafter by delivery or by writing of any kind pledged or assigned as and for
additional security hereunder, by the Issuer or by anyone on its behalf or with
its written consent, to the Trustee, which is hereby authorized to receive any
and all such property at any and all times and to hold and apply the same
subject to the terms hereof.

         TO HAVE AND TO HOLD all and singular the Trust Estate, whether now
owned or hereafter acquired, unto the Trustee and its respective successors in
said trusts and assigns forever.

         IN TRUST NEVERTHELESS, upon the terms and trusts herein set forth for
the equal and proportionate benefit, security and protection of all present and
future owners of the Bonds, from time to time issued under and secured by this
Indenture without privilege, priority or distinction as to the lien or otherwise
of any of the Bonds over any of the other Bonds (except only as otherwise
expressly stated herein).

         PROVIDED HOWEVER, that if the Issuer, its successors or assigns, shall
well and truly cause to be paid, the principal of the Bonds and the interest and
premium, if any, due or to become due thereon, at the times and in the manner
mentioned in the Bonds, according to the true intent and meaning thereof, and
shall cause the payments to be made into the Bond Fund as required under Article
V hereof or shall provide, as permitted by Article VII hereof, for the payment
thereof, and shall well and truly keep, perform and observe all the covenants
and conditions pursuant to the terms of this Indenture to be kept, performed and
observed by it, and shall pay or cause to be paid to the Trustee all sums of
money due or to become due in accordance with the terms and provisions hereof,
then this Indenture and the rights hereby granted shall cease, determine and be
void; otherwise this Indenture to be and remain in full force and effect.

         THIS INDENTURE OF TRUST FURTHER WITNESSETH, and it is expressly
declared, that all Bonds issued and secured hereunder are to be issued,
authenticated and delivered and the Revenues hereby assigned and pledged are to
be dealt with and disposed of under, upon and subject to the terms, conditions,
stipulations, covenants, agreements, trusts, uses and

                                      -10-
<PAGE>   15
purposes as hereinafter expressed, and the Issuer has agreed and covenanted, and
does hereby agree and covenant, with the Trustee and with the respective owners
from time to time of the Bonds, as follows:

                                    ARTICLE I

                                   DEFINITIONS

     SECTION 1.01. DEFINITIONS. (A) For all purposes of this Indenture, except
as otherwise expressly provided or unless the context otherwise requires:

                   (1) All references in this Indenture to designated
         "Articles", "Sections" and other subdivisions are to the designated
         Articles, Sections and other subdivisions of this Indenture.

                   (2) The words "herein", "hereof", "hereto", "hereby", and
         "hereunder" and other words of similar import refer to this Indenture
         as a whole and not to any particular Article, Section or other
         subdivision.

                   (3) The terms defined in this Article have the meanings
         assigned to them in this Article, and include the plural as well as the
         singular.

                   (4) All accounting terms not otherwise defined herein have
         the meanings assigned to them in accordance with generally accepted
         accounting principles as in effect from time to time.

                   (5) Every "request", "order", "demand", "application",
         "appointment", "notice", "statement", "certificate", "consent" or
         similar action hereunder by the Issuer shall, unless the form thereof
         is specifically provided, be in writing signed by the Authorized Issuer
         Representative.

                   (6) Every reference herein to the delivery of Bonds by the
         Trustee, or similar references, shall mean that Bonds shall be
         available to be picked up at the appointed time at the Corporate Trust
         Office of the Trustee.

                   (7) All other terms used herein which are defined in the
         Agreement shall have the same meanings assigned them in the Agreement
         unless the context otherwise requires.

         (B) For all purposes of this Indenture, except as otherwise expressly
provided or unless the context otherwise requires:

         "Act" means Title 35, Chapter 5, Arizona Revised Statutes, and all acts
supplementary thereto or amendatory thereof.

                                      -11-
<PAGE>   16
         "Administrative Expenses" means the reasonable and necessary expenses
(including the reasonable value of employee services and fees of Counsel)
incurred by the Issuer in connection with the Bonds, the Agreement, this
Indenture and any transaction or event contemplated by the Agreement or this
Indenture.

         "Agreement" means the Financing Agreement with respect to the Bonds of
even date herewith by and between the Issuer and the Company, as from time to
time amended and supplemented.

         "Authorized Company Representative" means any person who, at the time,
shall have been designated as such by a written certificate furnished to the
Issuer and the Trustee containing the specimen signature of such person and
signed on behalf of the Company by any officer of the Company. Such certificate
may designate an alternate or alternates.

         "Authorized Denominations" means $100,000 or any integral multiple
thereof.

         "Authorized Issuer Representative" means any person at the time
designated to act on behalf of the Issuer by a written certificate furnished to
the Company and the Trustee containing the specimen signature of such person and
signed on behalf of the Issuer by its President, Vice President, Secretary or
Assistant Secretary. Such certificate may designate an alternate or alternates.

         "Bond" or "Bonds" means any one or more of the bonds authorized,
authenticated and delivered under this Indenture.

         "Bond Counsel" means the Counsel who renders the opinion as to the
tax-exempt status of interest on the Bonds or other nationally recognized
municipal bond counsel mutually acceptable to the Issuer, the Trustee and the
Company.

         "Bond Fund" means the fund created by Section 5.02 hereof.

         "Bondholder" or "Holder" or "Owner" or "Owner of Bonds" means the
Person or Persons in whose name or names a Bond shall be registered on books of
the Issuer kept for that purpose in accordance with the terms of this Indenture.

         "Bond Registrar" means the Trustee.

         "Book Entry Bond" means a Bond authorized to be issued to and
restricted to being registered, in the name of, a Securities Depository as
provided in Section 2.09 hereof.

         "Business Day" means a day on which banks located in the city in which
the Corporate Trust Office of the Trustee is located are not required or
authorized to remain closed and on which the New York Stock Exchange is not
closed.

         "Code" means the United States Internal Revenue Code of 1986, as
amended, and regulations promulgated or proposed thereunder.

                                      -12-
<PAGE>   17
         "Company" means America West Airlines, Inc., a Delaware corporation,
and its successors and assigns and any surviving, resulting or transferee
corporation as permitted in Section 5.1 of the Agreement.

         "Corporate Trust Office" means the designated principal office of the
Trustee from which at any particular time its corporate trust business shall be
administered, which office at the date of original execution of this Indenture
is located at 3300 North Central Avenue, 15th Floor, Phoenix, Arizona 85012.

         "Counsel" means an attorney at law or a firm of attorneys (who may be
an employee of or counsel to the Issuer or the Company or the Trustee) duly
admitted to the practice of law before the highest court of any state of the
United States of America.

         "Dated Date" means April 1, 1998.

         "Default" or "event of default" means an occurrence or event specified
in and defined by Section 8.01 hereof.

         "DTC" means the Depository Trust Company, a limited purpose trust
company organized under the laws of the State of New York, and its successors
and assigns.

         "Executive Officer" means the President of the Governing Body of the
Issuer.

         "Extraordinary Services" and "Extraordinary Expenses" mean all services
rendered and all expenses (including fees of Counsel) incurred under the
Indenture and the Tax Agreement other than Ordinary Services and Ordinary
Expenses.

         "Governing Body" means the Board of Directors of the Issuer.

         "Government Obligations" means non-callable direct general obligations
of, or non-callable obligations the payment of the principal of and interest on
which are unconditionally guaranteed by, the United States of America.

         "Indenture" means this Indenture of Trust, including any indentures
supplemental hereto or amendatory hereof.

         "Interest Payment Date" means April 1 and October 1 of each year,
commencing October 1, 1998.

         "Issue Date" means April 2, 1998, the date of issuance and delivery of
the Bonds.

         "Issuer" means The Industrial Development Authority of the City of
Phoenix, Arizona and any successor body to the duties or functions of the
Issuer.

         "1954 Code" means the Internal Revenue Code of 1954, as amended.

                                      -13-
<PAGE>   18
         "Ordinary Services" and "Ordinary Expenses" mean those services
normally rendered and those expenses, including fees of Counsel, normally
incurred by a trustee, paying agent or bond registrar under instruments similar
to this Indenture and the Tax Agreement.

         "Original Purchaser" means Citicorp Securities, Inc.

         "Outstanding" or "outstanding" or "Bonds Outstanding", in connection
with the Bonds means, as of the time in question, all Bonds authenticated and
delivered under this Indenture, except:

                    A. Bonds theretofore cancelled or required to be cancelled
         under Section 2.07 hereof;

                    B. Bonds which are deemed to have been paid in accordance
         with Article VII hereof; and

                    C. Bonds in substitution for which other Bonds have been
         authenticated and delivered pursuant to Article II hereof.

         In determining whether the Owners of a requisite aggregate principal
amount of outstanding Bonds have concurred in any request, demand,
authorization, direction, notice, consent or waiver under the provisions of the
Indenture, Bonds which are owned of record by the Company or any affiliate
thereof or held by the Trustee for the account of the Company shall be
disregarded and deemed not to be Outstanding hereunder for the purpose of any
such determination (except that, in determining whether the Trustee shall be
protected in relying upon any such request, demand, authorization, direction,
notice, consent or waiver, only Bonds which the Trustee knows to be so owned or
held shall be disregarded) unless all Bonds are owned by the Company or any
affiliate thereof and/or held by the Trustee for the account of the Company, in
which case such Bonds shall be considered outstanding for the purpose of such
determination. For the purpose of this definition, an "affiliate" of any
specified Person means any other Person directly or indirectly controlling or
controlled by or under direct or indirect common control with such specified
Person and "control," when used with respect to any specified Person, means the
power to direct the management and policies of such Person, directly or
indirectly, whether through the ownership of voting securities, by contract or
otherwise; and the terms "controlling" and "controlled" have meanings
correlative to the foregoing.

         "Paying Agent" means the Trustee.

         "Person" means natural persons, firms, partnerships, associations,
corporations, trusts and public bodies.

         "Prior Bonds" has the meaning assigned to such term in the recitals to
this Indenture.

         "Prior Indenture" has the meaning assigned to such term in the recitals
to this Indenture.

                                      -14-
<PAGE>   19
         "Project" means the facilities described in Exhibit A to the Agreement.

         "Rebate Fund" means the Rebate Fund, if any, created and established
pursuant to the Tax Agreement and Section 5.13 hereof.

         "Record Date" means the fifteenth (15th) day of the calendar month
immediately preceding an Interest Payment Date, or if such day shall not be a
Business Day, the immediately preceding Business Day.

         "Recording Officer" means the Secretary of the Issuer.

         "Resolution" means the resolution duly adopted and approved by the
Governing Body of the Issuer on March 19, 1998 authorizing the issuance and sale
of the Bonds and the execution of this Indenture and the Agreement.

         "Revenues" means the amounts pledged hereunder to the payment of
principal of, and premium, if any, and interest on, the Bonds, consisting of the
following: (i) all amounts payable from time to time by the Company under
Section 4.2(a) of the Agreement, and all receipts of the Trustee credited under
the provisions of this Indenture against said amounts payable, and (ii) any
portion of the net proceeds of the Bonds deposited with the Trustee under
Section 5.03(a) hereof.

         "Securities Depository" means, with respect to a Book Entry Bond, DTC
or any person, firm, association or corporation constituting a "clearing agency"
(securities depository) registered under Section 17A of the Securities Exchange
Act of 1934, as amended, which may at any time be substituted in its place to
act as Securities Depository for the Bonds, or its successors, or any nominee
therefor.

         "State" means the State of Arizona.

         "Tax Agreement" means the Tax Exemption Certificate and Agreement with
respect to the Bonds, dated as of the date of the delivery of the Bonds, among
the Company, the Issuer and the Trustee, as from time to time amended and
supplemented.

         "Trust Estate" means the property conveyed to the Trustee pursuant to
the Granting Clauses hereof.

         "Trustee" means Norwest Bank Arizona, N.A., as trustee hereunder, and
any successor trustee pursuant to Section 9.06 or 9.09 hereof at the time
serving as successor Trustee hereunder, and any co-trustee serving as such
hereunder.

         "Written Consent of the Issuer," "Written Order of the Issuer,"
"Written Request of the Issuer" and "Written Requisition of the Issuer" mean,
respectively, a written consent, order, request or requisition signed by or on
behalf of the Issuer by an authorized Issuer Representative.

                                      -15-
<PAGE>   20
                                   ARTICLE II

                                    THE BONDS

                SECTION 2.01. AUTHORIZED AMOUNT AND PURPOSE OF BONDS. No Bonds
may be issued under the provisions of this Indenture except in accordance with
this Article. The total principal amount of Bonds that may be issued hereunder
is hereby expressly limited to $29,300,000 except as provided in Section 2.06
hereof. The Bonds shall be issued for the purpose of refinancing the cost of the
Project by refunding the Prior Bonds, as provided in the Agreement.

                SECTION 2.02. ISSUANCE OF BONDS. The Issuer may issue the Bonds
following the execution of this Indenture; and the Trustee shall, at the
Issuer's written request, authenticate such Bonds and deliver them as specified
in such request. The Bonds shall be designated "The Industrial Development
Authority of the City of Phoenix, Arizona Airport Facilities Refunding Bonds
(America West Airlines, Inc. Project) Series 1998." The Bonds shall be
substantially in the form hereinabove set forth with such appropriate
variations, omissions and insertions as are permitted or required by this
Indenture. The Bonds shall be issuable as fully registered bonds without coupons
in Authorized Denominations. Unless the Issuer shall otherwise direct, the Bonds
shall be numbered R-1 and upwards.

         Each Bond shall be dated as of April 1, 1998 and shall mature, subject
to prior redemption, upon the terms and conditions hereinafter set forth, on
April 1, 2023. The Bonds shall bear interest at the rate of six and three tenths
percent (6.30%) per annum from and including the date thereof until payment of
the principal or redemption price thereof shall have been made or provided for
in accordance with the provisions hereof, whether at maturity, upon redemption
or otherwise. Interest on the Bonds shall be computed upon the basis of a
360-day year, consisting of twelve (12) thirty (30) day months. Each Bond shall
bear interest on overdue principal and, to the extent permitted by law, on
overdue interest at the rate borne by the Bonds. The Trustee shall insert the
date of authentication of each Bond in the place provided for such purpose in
the form of certificate of authentication of Trustee to be printed on each Bond.

         The principal of, and premium, if any, and interest on, the Bonds shall
be payable in any coin or currency of the United States of America which, at the
respective dates of payment thereof, is legal tender for the payment of public
and private debts, and except as otherwise provided for Book Entry Bonds as
permitted by Section 2.09 hereof, such principal and premium, if any, shall be
payable at the Corporate Trust Office of the Trustee. Payment of interest on any
Interest Payment Date on any Bond shall be made to the Owner thereof as of the
close of business on the Record Date immediately prior thereto and except as
otherwise provided for Book Entry Bonds as permitted by Section 2.09 hereof,
shall be (i) made by check or draft mailed on the Interest Payment Date to such
Owner at his address as it appears on the registration books of the Issuer
maintained by the Trustee or at such other address as is furnished to the
Trustee in writing by such Owner not later than the close of business on such
Record Date or (ii) transmitted by wire transfer to an account with a commercial
bank located within the United States of America if such Owner owns at least

                                      -16-
<PAGE>   21
$1,000,000 in aggregate principal amount of the Bonds and shall have provided
wire transfer instructions to the Trustee prior to the close of business on such
Record Date, except that, if and to the extent that there shall be a default in
the payment of the interest due on such Interest Payment Date, such defaulted
interest shall be paid to the Owners in whose names any such Bonds are
registered at the close of business on the fifth Business Day next preceding the
date of payment of such defaulted interest.

         Interest on the Bonds shall be payable on each Interest Payment Date
for the period ending on the day immediately preceding such Interest Payment
Date and commencing on the immediately preceding Interest Payment Date, or if no
interest has been paid on the Bonds, on the date of the Bonds. Notwithstanding
the foregoing, if as shown by the records of the Trustee, interest on the Bonds
shall be in default, Bonds issued in exchange for Bonds surrendered for
registration of transfer or exchange shall bear interest from the date to which
interest has been paid in full on the Bonds, or if no interest has been paid on
the Bonds, from the date of the Bonds.

                SECTION 2.03. OWNERSHIP, TRANSFER, EXCHANGE AND REGISTRATION OF
BONDS. The Issuer shall cause books for the registration and for the transfer of
the Bonds as provided herein to be kept at the Corporate Trust Office of the
Trustee, which is hereby constituted and appointed the Bond Registrar and
transfer agent for the Bonds. The Issuer shall prepare and deliver to the
Trustee, and the Trustee shall keep custody of, a supply of forms of Bonds duly
executed by the Issuer, as provided in Section 2.04 hereof, for use in the
transfer and exchange of Bonds. The Trustee is hereby authorized and directed to
complete such forms of Bonds as to principal amounts and registered owners, in
accordance with the provisions hereof, in effecting transfers and exchanges of
Bonds as provided herein.

         Upon surrender for transfer of any Bond at the Corporate Trust Office
of the Trustee, duly endorsed for transfer or accompanied by a written
instrument or instruments of transfer in form satisfactory to the Trustee duly
executed by the Owner or his attorney duly authorized in writing, the Trustee
shall date and execute the certificate of authentication on and deliver in the
name of the transferee or transferees a new Bond or Bonds duly executed by the
Issuer of Authorized Denominations and for a like aggregate principal amount.

         Any Bond or Bonds may be exchanged at the Corporate Trust Office of the
Trustee for a new Bond or Bonds of like aggregate principal amount of other
Authorized Denominations. Upon surrender of any Bond or Bonds for exchange, the
Trustee shall date and execute the certificate of authentication on and deliver
a new Bond or Bonds duly executed by the Issuer which the Bondholder making the
exchange is entitled to receive.

         The Trustee shall not be required to transfer or exchange any Bond
after the mailing of notice calling such Bond or portion thereof for redemption,
nor during the period of fifteen days next preceding the mailing of such notice
of redemption.

         The person in whose name any Bond shall be registered shall be deemed
and regarded as the absolute owner thereof for all purposes, and payment of the
principal of, or premium,

                                      -17-
<PAGE>   22
if any, or interest on, any Bond shall be made only to or upon the written order
of the registered Owner thereof or his legal representative, but such
registration may be changed as hereinabove provided. All such payments shall be
valid and effective to satisfy and discharge the liability upon such Bond to the
extent of the sum or sums so paid.

         The Trustee shall require the payment by the Bondholder requesting
exchange or transfer (other than an exchange upon a partial redemption of a
Bond) of any tax, fee or other governmental charge required to be paid with
respect to such exchange or transfer, but otherwise no charge shall be made to
the Bondholder for such exchange or transfer.

                SECTION 2.04. EXECUTION; LIMITED OBLIGATION. The Bonds shall be
executed on behalf of the Issuer with the manual or facsimile signature of its
President and attested with the manual or facsimile signature of its Secretary.
All authorized facsimile signatures shall have the same force and effect as if
manually signed. The Bonds, together with interest thereon, are not general
obligations of the Issuer but are special, limited obligations payable solely
from the Revenues, and shall be a valid claim of the respective Owners thereof
only against the Bond Fund and the Revenues, which Revenues are hereby pledged,
assigned and otherwise secured for the equal and ratable payment of the Bonds
and shall be used for no other purpose than to pay the principal of, premium, if
any, and interest on the Bonds, except as may be otherwise expressly authorized
in this Indenture or the Tax Agreement. The Bonds and interest and premium, if
any, thereon shall never constitute the debt or indebtedness of the Issuer
within the meaning of any provision or limitation of the Constitution of the
State or statutes and shall not constitute nor give rise to a pecuniary
liability of the Issuer or a charge against its general credit. The Issuer has
no taxing power. In case any official of the Issuer whose signature or facsimile
of whose signature shall appear on the Bonds shall cease to be such official
before the delivery of such Bonds, such signature or such facsimile shall
nevertheless be valid and sufficient for all purposes, the same as if he had
remained in office until delivery.

                SECTION 2.05. AUTHENTICATION. No Bond shall be valid for any
purpose until the certificate of authentication on such Bond shall have been
duly executed by the Trustee, and such authentication shall be conclusive proof
that such Bond has been duly authenticated and delivered under this Indenture
and that the Owner thereof is entitled to the benefits of the trust hereby
created. The Trustee's certificate of authentication on any Bond shall be deemed
to have been executed by it if manually signed by an authorized signatory of the
Trustee, but it shall not be necessary that the same signatory sign the
certificate of authentication on all of the Bonds issued hereunder.

                SECTION 2.06. MUTILATED, DESTROYED, LOST OR STOLEN BONDS. In the
event any Bond or temporary Bond is mutilated, lost, stolen or destroyed, the
Trustee may authenticate a new Bond duly executed by the Issuer of like date and
denomination as that mutilated, lost, stolen or destroyed; provided that, in the
case of any mutilated Bond, such mutilated Bond shall first be surrendered to
the Trustee, and in the case of any lost, stolen or destroyed Bond, there shall
be first furnished to the Trustee evidence of such loss, theft or destruction
satisfactory to the Trustee, together with indemnity to the Issuer, the Trustee
and the Company satisfactory to them. In the event any such Bond shall have
matured or been

                                      -18-
<PAGE>   23
redeemed, instead of issuing a duplicate Bond, the Trustee on behalf of the
Issuer may pay the same without surrender thereof. The Issuer and the Trustee
may charge the Owner of such Bond with their reasonable fees and expenses in
this connection. The Issuer shall cooperate with the Trustee in connection with
the issue of replacement Bonds, but nothing in this Section shall be construed
in derogation of any rights which the Issuer, the Company or the Trustee may
have to receive indemnification against liability, or payment or reimbursement
of expenses, in connection with the issue of a replacement Bond. All Bonds shall
be held and owned upon the express condition that the foregoing provisions are,
to the extent permitted by law, exclusive with respect to the replacement or
payment of mutilated, destroyed, lost or stolen Bonds, and shall preclude any
and all other rights or remedies.

                SECTION 2.07. CANCELLATION AND DESTRUCTION OF SURRENDERED BONDS.
Whenever any Outstanding Bond shall be delivered to the Trustee for transfer,
exchange or cancellation pursuant to this Indenture, upon payment of the
principal amount represented thereby, or for replacement pursuant to Section
2.06 hereof, such Bond shall be promptly cancelled and cremated or otherwise
destroyed by the Trustee.

                SECTION 2.08. DELIVERY OF THE BONDS. Upon the execution and
delivery of this Indenture, the Issuer shall execute and deliver to the Trustee
and the Trustee shall authenticate the Bonds and deliver them to the Original
Purchasers as directed by the Issuer as hereinafter in this Section provided.

         Prior to the delivery by the Trustee of any of the Bonds there shall be
filed with the Trustee:

                   (1) A duly certified copy of the Resolution.

                   (2) Original executed counterparts of the Agreement, the Tax
         Agreement and this Indenture.

                   (3) An opinion of Bond Counsel to the effect that the Bonds
         have been validly issued under this Indenture and that all requirements
         under this Indenture precedent to the delivery of the Bonds have been
         satisfied.

                   (4) A request and authorization to the Trustee on behalf of
         the Issuer and signed by the Executive Officer to authenticate and
         deliver the Bonds to or as directed by the Original Purchaser,
         registered in the names and in the Authorized Denominations specified
         to the Trustee by the Original Purchaser, upon payment by the Original
         Purchaser of a sum specified in such request to the Trustee (such sum
         to be applied in accordance with the Written Order of the Issuer
         furnished to the Trustee on the Issue Date), plus accrued interest, if
         any, on the Bonds to the date of delivery (which accrued interest shall
         be deposited in the Bond Fund).

                   (5) Original executed Investor Letter(s) in the form attached
         as Exhibit I hereto.

                                      -19-
<PAGE>   24
                SECTION 2.09. BOOK ENTRY SYSTEM. The Trustee and the Issuer (or
the Issuer with advice to the Trustee), at the direction of the Company, may
from time to time enter into, and discontinue, an agreement with a "clearing
agency" (securities depository) registered under Section 17A of the Securities
Exchange Act of 1934, as amended (the "Securities Depository"), which is the
owner of the Bonds, to establish procedures with respect to the Bonds not
inconsistent with the provisions of this Indenture; provided, however, that,
notwithstanding any other provisions of this Indenture, any such agreement may
provide:

                   (a) that the Securities Depository is not required to present
         a Bond to the Trustee in order to receive a partial payment of
         principal;

                   (b) that different provisions for notice to such Securities
         Depository may be set forth therein; and

                   (c) that a legend shall appear on each Bond so long as the
         Bonds are subject to such agreement.

         With respect to Bonds registered in the name of a Securities Depository
(or its nominee) neither the Trustee, the Issuer nor the Company shall have any
obligation to any of its members or participants or to any person on behalf of
whom an interest is held in the Bonds.

         It is hereby acknowledged that the Issuer has entered into an agreement
(the "Letter of Representation") with DTC which applies to the Bonds, and while
the Letter of Representations is in effect, the procedures established by DTC
shall apply to the Bonds notwithstanding any other provisions of this Indenture
to the contrary. As long as DTC is the Securities Depository with respect to the
Bonds, the Trustee shall be a DTC Participant.

                                   ARTICLE III

                       REDEMPTION OF BONDS BEFORE MATURITY

                SECTION 3.01. OPTIONAL REDEMPTION. The Bonds shall be subject to
redemption, at the option of the Company, prior to maturity on or after April 1,
2008, in whole or in part on the dates set forth below, at the redemption prices
(expressed as percentages of the principal amount) set forth in the following
table, plus accrued interest, if any, to the redemption date:


<TABLE>
<CAPTION>
                              Redemption Dates                                                Redemption Prices
                              ----------------                                                -----------------
<S>               <C>                                                                         <C>
                  April 1, 2008 and October 1, 2008                                                    102%

                  April 1, 2009 and October 1, 2009                                                    101%
</TABLE>

                                      -20-
<PAGE>   25
<TABLE>
<CAPTION>
<S>               <C>                                                                         <C>
                  April 1, 2010 and any Interest Payment Date thereafter.                              100%
</TABLE>

                SECTION 3.02. RESERVED.

                SECTION 3.03. MANDATORY REDEMPTION. The Bonds shall be subject
to mandatory redemption prior to maturity in whole, or as hereafter provided in
part, at any time prior to their maturity at a redemption price equal to 100% of
the principal amount thereof plus accrued interest, if any, to the redemption
date, not more than one hundred eighty (180) days after (i) receipt by the
Company of written notice of the issuance of a private letter ruling or a
technical advice memorandum by the Internal Revenue Service in a proceeding in
connection with which the Company has had the opportunity to participate or (ii)
the Company receives written notice of a final determination by any court of
competent jurisdiction of the United States in a proceeding to which the Company
is a party or in which the Company has had the opportunity to participate, in
either case, to the effect that, as a result of a failure by the Company to
observe any covenant, agreement, representation or warranty in the Agreement or
the Project Certificate, the interest payable on the Bonds is included in the
gross income for federal income tax purposes of the Owners or beneficial owners
thereof (other than a person who is a "substantial user" of the Project or a
"related person" within the meaning of Section 147(a) of the Code or Section
103(b)(13) of the 1954 Code). Upon the occurrence of any event described in the
first sentence of this Section 3.03, the Bonds shall be redeemed in whole
unless, in the opinion of Bond Counsel, the redemption of a portion of the
Outstanding Bonds would have the result that interest payable on the Bonds
remaining Outstanding after such redemption would not be included in the gross
income for federal income tax purposes of any Owners or beneficial owners of the
Bonds (other than a person who is a "substantial user" of the Project or a
"related person" within the meaning of Section 147(a) of the Code or Section
103(b)(13) of the Prior Code), in which event only such portion of the
Outstanding Bonds shall be redeemed.

                SECTION 3.04. NOTICE OF REDEMPTION. Upon receipt of notice given
by the Company pursuant to Section 7.3 of the Agreement, notice of the call for
any redemption of Bonds or any portions thereof pursuant to Section 3.01 or 3.03
hereof identifying the Bonds or portions thereof to be redeemed, specifying the
redemption date, the redemption price, the place and manner of payment and that
from the redemption date interest will cease to accrue (provided that funds for
the redemption of such Bonds or portions thereof are on deposit with the Trustee
on such redemption date) shall be given by the Trustee by mailing a copy of the
redemption notice by first-class mail to the Owner of each Bond to be redeemed
in whole or in part at the address shown on the registration books; provided,
however, except in the case of a conditional notice of optional redemption as
described in the next succeeding paragraph, the Trustee shall not give any
notice of redemption unless funds sufficient for such redemption are then on
deposit with the Trustee. Notice of redemption shall be provided at least thirty
(30) days prior to the date fixed for redemption to the Owners of Bonds to be
redeemed; provided, however, that failure to duly give such notice, or any
defect therein, shall not affect the validity of any proceedings for the
redemption of Bonds with respect to which no such failure or defect occurred.
Upon presentation and

                                      -21-
<PAGE>   26
surrender of Bonds so called for redemption in whole or in part at the place or
places of payment, such Bonds or portions thereof shall be redeemed.

         With respect to any notice of optional redemption of Bonds, unless upon
the giving of such notice such Bonds shall be deemed to have been paid within
the meaning of Article VII hereof, such notice may state (if so directed by the
Company in writing) that such redemption shall be conditioned upon the receipt
by the Trustee on or prior to the date fixed for such redemption of moneys
sufficient to pay the principal of, and premium, if any, and interest on, such
Bonds to be redeemed, and that if such moneys shall not have been so received
said notice shall be of no force and effect and the Issuer shall not be required
to redeem such Bonds. In the event that such notice of redemption contains such
a condition and such moneys are not so received, the redemption shall not be
made and the Trustee shall within a reasonable time thereafter give notice, in
the manner in which the notice of redemption was given, that such moneys were
not so received.

         Any notice mailed as provided in this Section shall be conclusively
presumed to have been duly given, whether or not the Owner receives the notice.

         In addition to the foregoing notice, further notice may be given by the
Trustee as set out below, but no defect in said further notice nor any failure
to give all or any portion of such further notice shall in any manner defeat the
effectiveness of a call for redemption if notice thereof is given as above
prescribed.

            A. Each further notice of redemption given hereunder shall contain
the information required above for an official notice of redemption plus (i) the
CUSIP number of the Bonds; (ii) the Dated Date of the Bonds; (iii) the rate of
interest borne by the Bonds; (iv) the maturity date of the Bonds; and (v) any
other descriptive information needed to identify accurately the Bonds being
redeemed.

            B. Each further notice of redemption shall be sent at least five
days before the date the redemption notice to the Owners is required to be given
as provided in the first paragraph of this Section 3.04, by registered or
certified mail or overnight delivery service, to all registered securities
depositories then in the business of holding substantial amounts of obligations
of types comprising the Bonds (such depositories now being Depository Trust
Company of New York, New York; Midwest Securities Trust Company of Chicago,
Illinois; Pacific Securities Depository Trust Company of San Francisco,
California; and Philadelphia Depository Trust Company of Philadelphia,
Pennsylvania).

            C. Each further notice of redemption may be published one time in
the Bond Buyer of New York, New York or, if such publication is impractical, in
some other financial newspaper or journal which regularly carries notices of
redemption of other obligations similar to the Bonds, such publication to be
made at the time the redemption notice to the Owners is required to be given as
provided in the first paragraph of this Section 3.04.

                                      -22-
<PAGE>   27
            D. Each further notice of redemption shall be given at least two
days before the date the redemption notice to the Owners is required to be given
as provided in the first paragraph of this Section 3.04, by (i) registered or
certified mail, postage prepaid, or (ii) overnight delivery service, to two of
the following services selected by the Company and at the address provided to
the Trustee by the Company:

                   (1)     Financial Information, Inc.'s Financial Daily Called
                           Bond Service;

                   (2)     Interactive Data Corporation's Bond Service;

                   (3)     Kenny Information Service's Called Bond Service;

                   (4)     Moody's Municipal and Government Called Bond Service;
                           or

                   (5)     Standard & Poor's Called Bond Record.

         The Company shall pay, or shall reimburse the Trustee for payment of,
all costs and expenses of redeeming Bonds.

                SECTION 3.05. DEPOSIT OF FUNDS. For the redemption of any of the
Bonds, the Issuer shall cause to be deposited in the Bond Fund out of the
Revenues moneys sufficient to pay when due the principal of, and premium, if
any, and interest on, the Bonds or portions thereof to be redeemed on the
redemption date. Moneys in the Bond Fund which are available therefor shall be
credited against any moneys which the Issuer is required to cause to be so
deposited in the Bond Fund.

                SECTION 3.06. PARTIAL REDEMPTION OF BONDS. In case a Bond is of
a denomination larger than the minimum Authorized Denomination, all or a portion
of such Bond may be redeemed in an Authorized Denomination. Upon surrender of
any Bond for redemption in part only, the Issuer shall execute and the Trustee
shall authenticate and deliver to the Owner thereof, without cost to the Owner,
a new Bond or Bonds of Authorized Denominations in aggregate principal amount
equal to the unredeemed portion of the Bond surrendered.

                SECTION 3.07. SELECTION OF BONDS FOR REDEMPTION. If less than
all of the Bonds are called for redemption, the Trustee shall select the Bonds
or portions thereof to be redeemed from the Bonds outstanding not previously
called for redemption, in such manner as in the Trustee's sole discretion it
shall deem appropriate and fair. If it is determined that one or more, but not
all, of the portions of principal amount represented by any such Bond is to be
called for redemption, then, upon notice of intention to redeem such portion or
portions, the Owner of such Bond shall forthwith surrender such Bond to the
Trustee for (a) payment to such Owner of the redemption price of the portion or
portions of principal amount called for redemption, and (b) delivery to such
Owner of a new Bond or Bonds in the aggregate principal amount of the unredeemed
portion of the principal amount of such Bond. New Bonds representing the
unredeemed portion of the principal amount of such Bond shall be issued to the
Owner thereof, without charge therefor. If the Owner of any

                                      -23-
<PAGE>   28
such Bond shall fail to present such Bond to the Trustee for payment and
exchange as aforesaid, such Bond shall, nevertheless, become due and payable on
the date fixed for redemption to the extent of the portion or portions of
principal amount called for redemption (and to that extent only) and interest
with respect to such portion or portions will cease to accrue.

                                   ARTICLE IV

                           PAYMENT; FURTHER ASSURANCES

                SECTION 4.01. PAYMENT OF PRINCIPAL OR REDEMPTION PRICE OF AND
INTEREST ON BONDS. The Issuer shall promptly pay or cause to be paid the
principal of, and premium, if any, and interest on, every Bond issued hereunder
according to the terms thereof, but shall be required to make such payment or
cause such payment to be made only out of Revenues. The Issuer hereby appoints
the Trustee to act as the Paying Agent for the Bonds and designates the
Corporate Trust Office of the Trustee as the place of payment of principal and
premium, if any, of the Bonds.

                SECTION 4.02. PERFORMANCE OF COVENANTS; THE ISSUER. The Issuer
covenants that it will faithfully perform at all times any and all covenants,
undertakings, stipulations and provisions contained in this Indenture, in any
and every Bond executed, authenticated and delivered hereunder and in all of its
proceedings pertaining thereto; provided, however, that except for the matters
set forth in Section 4.01 hereof the Issuer shall not be obligated to take any
action or execute any instrument pursuant to any provision hereof until it shall
have been requested to do so by the Company, or shall have received the
instrument to be executed and at the Issuer's option shall have received from
the Company assurance satisfactory to Issuer that the Issuer shall be reimbursed
for its reasonable expenses incurred or to be incurred in connection with taking
such action or executing such instrument. The Bonds and interest and premium, if
any, thereon, and any obligation of the Issuer under the Agreement or this
Indenture, shall never constitute a debt or indebtedness of the Issuer within
the meaning of any constitutional or statutory provision or limitation and shall
not constitute nor give rise to a pecuniary liability of the Issuer or a charge
against its general credit. The Issuer has no taxing power.

                SECTION 4.03. RIGHT TO PAYMENTS UNDER AGREEMENT; INSTRUMENTS OF
FURTHER ASSURANCE. The Issuer covenants that it will defend its right to the
payment of amounts due from the Company under the Agreement to the Trustee, for
the benefit of the Owners of the Bonds against the claims and demands of all
persons whomsoever. Notwithstanding the foregoing, the Issuer shall not be
obligated to take any action under this Section 4.03 unless the Issuer receives
satisfactory indemnification for the reimbursement of all expenses to which it
may be put and to protect it against all liability. The Issuer covenants that it
will do, execute, acknowledge and deliver or cause to be done, executed,
acknowledged and delivered, such indentures supplemental hereto and such further
acts, instruments and transfers as the Trustee may reasonably require for the
better assuring, transferring, conveying, pledging, assigning and confirming
unto the Trustee all and

                                      -24-
<PAGE>   29
singular the rights assigned hereby and the amounts pledged hereto, to the
payment of the principal of, and premium, if any, and interest on, the Bonds.
The Issuer covenants and agrees that, except as herein and in the Agreement and
the Tax Agreement provided, it will not sell, convey, mortgage, encumber or
otherwise dispose of any part of the Revenues or its rights under the Agreement.

         No provision of this Indenture shall require the Issuer to expend or
risk its own funds or otherwise incur any financial liability in the performance
of any of its duties hereunder, or in the exercise of any of its rights or
powers, if it believes that repayment of such funds or adequate indemnity
against such risk or liability is not assured to it.

                SECTION 4.04. FINANCING STATEMENTS. The Issuer shall cause a
financing statement related to this Indenture to be filed at the time of
execution and delivery of the Bonds. The Company shall provide to the Trustee
thirty days prior to the sixth anniversary of such financing statement (or any
continuation statement with respect thereto) a certificate as to whether a
continuation statement under Arizona Revised Statutes Section 47-9403B is
required to be filed to continue the effectiveness of the financing statement
and if a continuation statement is required, the Company shall provide the
completed continuation statement to the Trustee. The Trustee and the Issuer
shall, if necessary, execute or join in the execution of the continuation
statement and file or join in the filing thereof at such time or times and in
such place or places as it may be advised by said certificate will preserve the
effectiveness of the financing statement until the principal and interest on the
Bonds shall have been paid or provided for. The Trustee shall, to the extent
reasonably possible, take such actions as may be specified in such certificate,
but shall have no further obligation or responsibility to take any other actions
to preserve the lien of this Indenture upon the Trust Estate or any part
thereof.

                SECTION 4.05. INSPECTION OF PROJECT BOOKS. The Issuer and the
Trustee covenant and agree that all books and documents in their possession
relating to the Project and the Revenues derived from the Project shall at all
times be open to inspection by such accountants or other agencies as the other
party may from time to time designate.

                SECTION 4.06. RIGHTS UNDER AGREEMENT. The Agreement, a duly
executed counterpart of which has been filed with the Trustee, sets forth the
covenants and obligations of the Issuer and the Company, and reference is hereby
made to the same for a detailed statement of said covenants and obligations of
the Company thereunder, and the Issuer agrees that the Trustee in its name or in
the name of the Issuer may enforce all rights of the Issuer and all obligations
of the Company under and pursuant to the Agreement for and on behalf of the
Bondholders, whether or not the Issuer is in default hereunder. Nothing herein
contained shall be construed to prevent the Issuer from enforcing directly any
and all of its rights under Sections 4.2(d), 4.2(e), 5.3 and 6.4 of the
Agreement.

                                      -25-
<PAGE>   30
                                   ARTICLE V

                               REVENUES AND FUNDS

                SECTION 5.01. SOURCE OF PAYMENT OF BONDS. The Bonds and all
payments required of the Issuer hereunder are not general obligations of the
Issuer but are limited obligations as described in Section 2.04 hereof. The
Revenues are pledged and assigned to the payment of the principal of, and
premium, if any, and interest on, the Bonds. The payments provided in Sections
4.2(a) of the Agreement are to be remitted directly to the Trustee and deposited
in the Bond Fund. Such payments, sufficient in amount to insure the prompt
payment of the principal of, and premium, if any, and interest on, the Bonds,
are pledged to such payment.

                SECTION 5.02. CREATION OF THE BOND FUND. There is hereby created
by the Issuer and ordered established with the Trustee a trust fund to be
designated "The Industrial Development Authority of the City of Phoenix, Arizona
- Airport Facilities Refunding Bond Fund - America West Airlines, Inc. Project -
Series 1998", which shall be used to pay the principal of, and premium, if any,
and the interest on, the Bonds.

                SECTION 5.03. PAYMENTS INTO THE BOND FUND. There shall be
deposited into the Bond Fund from time to time the following:

                   (a) all accrued interest, if any, paid by the Original
         Purchaser of the Bonds;

                   (b) all payments specified in Section 4.2 (a) of the
         Agreement; and

                   (c) all other moneys received by the Trustee under and
         pursuant to any of the provisions of the Agreement or otherwise, when
         accompanied by directions from the person depositing such moneys that
         such moneys are to be paid into the Bond Fund.

         The Issuer hereby covenants and agrees that so long as any of the Bonds
issued hereunder are outstanding it will cause to be deposited in the Bond Fund
sufficient amounts from Revenues promptly to meet and pay the principal of, and
premium, if any, and interest on, the Bonds as the same become due and payable.
Nothing herein shall be construed as requiring the Issuer to use any funds or
revenues from any source other than Revenues.

                SECTION 5.04. USE OF MONEYS IN THE BOND FUND. Except as provided
in Sections 5.06, 5.09 and 9.03 hereof, moneys in the Bond Fund shall be used
solely for the payment of the principal of, and premium, if any, and interest
on, the Bonds as the same shall become due and payable at maturity, upon
redemption or otherwise.

                SECTION 5.05. CUSTODY OF THE BOND FUND. The Bond Fund shall be
in the custody of the Trustee, and the Issuer hereby authorizes and directs the
Trustee to withdraw sufficient funds from the Bond Fund to pay the principal of,
and premium, if any, and interest on, the Bonds as the same become due and
payable and to comply with Article VI of the Tax Agreement, which authorization
and direction the Trustee hereby accepts.

                                      -26-
<PAGE>   31

      SECTION 5.06. NON-PRESENTMENT OF BONDS. In the event any Bond shall not be
presented for payment when the principal thereof becomes due, either at maturity
or otherwise, or on the date fixed for the redemption thereof, or in the event
any interest payment thereon is unclaimed, if moneys sufficient to pay such Bond
and premium, if any, or interest shall have been deposited in the Bond Fund, all
liability of the Issuer to the Owner thereof for the payment of such Bond and
premium, if any, or interest shall forthwith cease, determine and be completely
discharged, and thereupon it shall be the duty of the Trustee to hold such
moneys, without liability for interest thereon, for the benefit of the Owner of
such Bond who shall thereafter be restricted exclusively to such moneys, for any
claim of whatever nature on his part under this Indenture or on, or with respect
to, said Bond. Any moneys so deposited with and held by the Trustee not so
applied to the payment of Bonds and premium, if any, or interest, if any, within
one (1) year after the date on which the same shall have become due shall be
paid by the Trustee to the Company upon the written direction of an Authorized
Company Representative and thereafter Owners shall be entitled to look only to
the Company for payment, and then only to the extent of the amount so repaid,
and the Company shall not be liable for any interest thereon and shall not be
regarded as a trustee of such moneys and the Trustee shall have no further
responsibility with respect to such moneys.

      SECTION 5.07. TRUSTEE'S FEES, CHARGES AND EXPENSES. The Trustee agrees
that the Issuer shall have no liability for any fees, charges and expenses of
the Trustee, and the Trustee agrees to look only to the Company for the payment
of all fees, charges and expenses of the Trustee as provided in the Agreement
and in this Indenture.

      SECTION 5.08. MONEYS TO BE HELD IN TRUST. All moneys and securities held
by the Trustee in the Bond Fund, all moneys required to be deposited with or
paid to the Trustee for deposit into the Bond Fund under any provision hereof,
all moneys withdrawn from the Bond Fund and held by the Trustee, shall be held
by the Trustee in trust, and such moneys (other than as provided in Sections
5.06 and 5.12 hereof and subject to the provisions of the Tax Agreement as
provided in Section 5.13 hereof) shall, while so held, constitute part of the
Trust Estate and be subject to the lien hereof.

      SECTION 5.09. REPAYMENT TO THE COMPANY FROM THE BOND FUND. Any amounts
remaining in the Bond Fund after payment in full of the principal of, and
premium, if any, and interest on, the Bonds (or provision for payment thereof as
provided in this Indenture), the fees, charges and expenses of the Issuer and
the Trustee and all other amounts required to be paid under the Agreement and
this Indenture shall be paid to the Company as provided in Section 8.5 of the
Agreement, subject to the provisions of the Tax Agreement.

      SECTION 5.10. REVENUES TO BE PAID OVER TO TRUSTEE. The Issuer will cause
the Revenues to be paid to the Trustee for deposit in the Bond Fund in
accordance with the terms of this Indenture to effect payment of the principal
of, and premium, if any, and interest on, the Bonds as the same become due.


                                      -27-
<PAGE>   32
      SECTION 5.11. PAYMENTS OF PRINCIPAL AND INTEREST. The Trustee shall pay
from Revenues received by the Trustee the principal of, and premium, if any, and
interest on, the Bonds as the same become due and payable.

      SECTION 5.12. REVENUES TO BE HELD FOR ALL BONDHOLDERS; CERTAIN EXCEPTIONS.
Revenues and investments thereof shall, until applied as provided in this
Indenture, be held by the Trustee for the benefit of the Owners of all
Outstanding Bonds (except as provided by Section 5.06 hereof), except that any
portion of the Revenues representing principal of, and premium, if any, and
interest on, any Bonds previously called for redemption in accordance with
Article III of this Indenture shall be held for the benefit of the Owners of
such Bonds only and shall not be deposited or invested pursuant to Article VI
hereof, notwithstanding any provision of Article VI.

      SECTION 5.13. TAX AGREEMENT. Notwithstanding anything in the Agreement or
this Indenture to the contrary, the Trustee is hereby authorized to deposit
moneys in the Bond Fund and to withdraw moneys from the Bond Fund, and to
establish and administer the Rebate Fund, if any, in order to comply with the
provisions of the Tax Agreement.

      SECTION 5.14. COST OF ISSUANCE FUND. The Trustee is authorized to create a
Costs of Issuance Fund to be funded solely from amounts paid by the Company.
Amounts in such Fund shall be disbursed at the written direction of the Company.
The Issuer shall direct the Trustee in writing on the date of issuance of the
Bonds as to whether such fund shall be created.

                                   ARTICLE VI

                              INVESTMENT OF MONEYS

      SECTION 6.01. INVESTMENT OF BOND FUND MONEYS. Subject to the provisions of
the Tax Agreement and Sections 5.06 and 5.12 hereof, any moneys held as part of
the Bond Fund, shall be invested and reinvested by the Trustee at the direction
of the Company in accordance with the provisions of Section 3.5 of the
Agreement. Any such investments shall be held by or under the control of the
Trustee and shall be deemed at all times a part of the Bond Fund. The interest
accruing thereon, any profit realized from such investments and any loss
resulting from such investments shall be credited or charged to such fund in
accordance with Section 3.5 of the Agreement. The Trustee shall sell and reduce
to cash a sufficient amount of such investments in the Bond Fund whenever the
cash balance in the Bond Fund is insufficient to pay the principal of, and
premium, if any, and interest on, the Bonds when due and whenever required in
order to comply with the provisions of the Tax Agreement.

      SECTION 6.02. INVESTMENTS; ARBITRAGE. The Trustee may make any and all
investments permitted by the provisions of Section 6.01 hereof through its own
investment department or that of an affiliate. The Company has covenanted in
Section 3.6 of the Agreement that none of the proceeds of the Bonds or the
payments to be made under the


                                      -28-
<PAGE>   33
Agreement, or any other funds which may be deemed to be proceeds of the Bonds
pursuant to Section 148(a) of the Code, will be invested in such a way as to
cause the Bonds to be treated as "arbitrage bonds" within the meaning of Section
148(a) of the Code.

                                   ARTICLE VII

                                   DEFEASANCE

      SECTION 7.01. DEFEASANCE. If the Issuer shall pay or cause to be paid, or
there shall be otherwise paid or provision for payment made to or for the Owners
of the Bonds the principal, premium, if any, and interest due or to become due
thereon at the times and in the manner stipulated therein, and if the Issuer
shall keep, perform and observe all and singular the covenants and promises in
the Bonds and in this Indenture expressed as to be kept, performed and observed
by it or on its part, and shall pay or cause to be paid to the Trustee all sums
of money due or to become due according to the provisions hereof, then this
Indenture and the lien, rights and interests created hereby shall cease,
determine and become null and void (except as to any surviving rights of
payment, registration, transfer or exchange of Bonds herein provided for),
whereupon the Trustee upon written request of an Authorized Issuer
Representative shall cancel and discharge this Indenture, and execute and
deliver to the Issuer such instruments in writing as shall be requested by an
Authorized Issuer Representative and requisite to discharge this Indenture, and
release, assign and deliver unto the Issuer any and all of the estate, right,
title and interest in and to any and all rights assigned or pledged to the
Trustee or otherwise subject to this Indenture, except amounts in the Bond Fund
required to be paid to the Company under Section 5.09 hereof and except moneys
or securities held by the Trustee for the payment of the principal of and
premium, if any, and interest on the Bonds and except for any amounts required
to be transferred to the Rebate Fund.

      Any Bond or Authorized Denomination thereof shall be deemed to be paid
within the meaning of this Indenture when (a) payment of the principal of, and
premium, if any, on, such Bond or Authorized Denomination thereof, plus interest
thereon to the due date thereof (whether such due date is by reason of maturity
or upon redemption as provided herein) either (i) shall have been made or caused
to be made in accordance with the terms thereof or (ii) shall have been provided
for by irrevocably depositing with the Trustee in trust and irrevocably set
aside exclusively for such payment (1) moneys sufficient to make such payment
and/or (2) Government Obligations maturing as to principal and interest in such
amount and at such time as will insure the availability of sufficient moneys to
make such payment, and (b) all necessary and proper fees, compensation and
expenses of the Trustee pertaining to any such deposit shall have been paid or
the payment thereof provided for to the satisfaction of the Trustee. At such
times as a Bond or Authorized Denomination thereof shall be deemed to be paid
hereunder, as aforesaid, such Bond or Authorized Denomination thereof shall no
longer be secured by or entitled to the benefits of this Indenture (except as to
any surviving rights to payment, registration of transfer, exchange or
replacement of Bonds herein provided for, and except for the purposes of any
such payment from such moneys or Government Obligations).


                                      -29-
<PAGE>   34
      Notwithstanding the foregoing paragraph, in the case of a Bond or
Authorized Denomination thereof which by its terms may be redeemed prior to the
stated maturity thereof, no deposit under clause (a)(ii) of the immediately
preceding paragraph shall be deemed a payment of such Bond or Authorized
Denomination thereof as aforesaid until proper notice of redemption of such Bond
or Authorized Denomination thereof shall have been previously given in
accordance with Article III of this Indenture, or in the event said Bond or
Authorized Denomination thereof is not to be redeemed within the next succeeding
sixty (60) days, until the Company shall have given the Trustee on behalf of the
Issuer, in form satisfactory to the Trustee, irrevocable instructions to notify,
as soon as practicable, the Owner of such Bond or Authorized Denomination
thereof in accordance with Article III hereof, that the deposit required by
(a)(ii) above has been made with the Trustee and that said Bond or Authorized
Denomination thereof is deemed to have been paid in accordance with this Article
and stating the maturity or redemption date upon which moneys are to be
available for the payment of the principal of and the applicable premium, if
any, on said Bond or Authorized Denomination thereof, plus interest thereon to
the due date thereof.

      Notwithstanding any provision of any other Article of this Indenture which
may be contrary to the provisions of this Article, all moneys or Government
Obligations set aside and held in trust pursuant to the provisions of this
Article for the payment of Bonds or Authorized Denominations thereof (including
interest and premium thereon, if any) shall be applied to and used solely for
the payment of the particular Bonds or Authorized Denominations thereof
(including interest and premium thereon, if any) with respect to which such
moneys and Government Obligations have been so set aside in trust.

      Anything in Article X hereof to the contrary notwithstanding, if moneys or
Government Obligations have been deposited or set aside with the Trustee
pursuant to this Article for the payment of Bonds or Authorized Denominations
thereof and the interest and premium, if any, thereon and such Bonds or
Authorized Denominations thereof and the interest and premium, if any, thereon
shall not have in fact been actually paid in full, no amendment to the
provisions of this Article shall be made without the consent of the Owner of
each of the Bonds affected thereby.

                                  ARTICLE VIII

                          DEFAULT PROVISIONS; REMEDIES

      SECTION 8.01. DEFAULTS; EVENTS OF DEFAULT. If any of the following events
occurs, it is hereby defined as and declared to be and to constitute a default
or an event of default:

            (a) Failure to make due and punctual payment of any installment of
      interest on any Bond when the same shall have become due and payable and
      the continuation of such failure for a period of two (2) Business Days
      after such payment has become due and payable;


                                      -30-
<PAGE>   35
            (b) Failure to make due and punctual payment of the principal of and
      premium, if any, on any Bond at the stated maturity thereof, or upon
      proceedings for the unconditional redemption thereof;

            (c) The occurrence of an "event of default" under the Agreement;

            (d) Failure on the part of the Issuer to perform or observe any of
      its covenants, agreements or conditions in this Indenture or in the Bonds
      contained and failure to remedy the same after notice thereof pursuant to
      Section 8.10 hereof.

      SECTION 8.02. ACCELERATION. Upon the occurrence of an event of default
under Section 8.01 the Trustee may, and upon the written request of the Owners
of not less than a majority in aggregate principal amount of Bonds then
outstanding shall, declare the principal of all Bonds then outstanding and the
interest accrued thereon immediately due and payable, and such principal and
interest shall thereupon become and be immediately due and payable. The Trustee
shall immediately thereafter give notice of such declaration to the Company and
the Issuer. After such declaration of acceleration the Trustee shall immediately
declare all indebtedness payable under Section 4.2(a) of the Agreement to be
immediately due and payable in accordance with Section 6.2 of the Agreement.

      The above provisions are subject to waiver, rescission and annulment as
provided in Section 8.09 hereof.

      SECTION 8.03. REMEDIES; RIGHTS OF BONDHOLDERS. Upon the occurrence and
continuation of an event of default the Trustee may pursue any available remedy
at law or in equity by suit, action, mandamus or other proceeding to enforce the
payment of the principal of, and premium, if any, and interest on, the Bonds
then outstanding, and to enforce and compel the performance of the duties and
obligations of the Issuer as herein set forth. In addition, the Trustee may,
without notice to the Issuer or the Company, exercise any and all remedies
afforded the Issuer under Article VI of the Agreement in its name or the name of
the Issuer without the necessity of joining the Issuer.

      If an event of default shall have occurred and be continuing and if
requested so to do by the Owners of not less than a majority in aggregate
principal amount of Bonds then outstanding and upon being indemnified as
provided in Section 9.01(i) hereof, the Trustee shall be obligated to exercise
such one or more of the rights and powers conferred by this Section 8.03 and
Section 8.02 hereof as the Trustee being advised by Counsel shall deem most
expedient in the interests of the Bondholders.

      No remedy by the terms of this Indenture conferred upon or reserved to the
Trustee (or to the Bondholders) is intended to be exclusive of any other remedy,
but each and every such remedy shall be cumulative and shall be in addition to
any other remedy given to the Trustee or to the Bondholders hereunder or now or
hereafter existing at law or in equity or by statute.


                                      -31-
<PAGE>   36
      No delay or omission to exercise any right, power or remedy accruing upon
any event of default shall impair any such right, power or remedy or shall be
construed to be a waiver of any such event of default or acquiescence therein;
and every such right, power or remedy may be exercised from time to time and as
often as may be deemed expedient.

      No waiver of any event of default hereunder, whether by the Trustee or by
the Bondholders, shall extend to or shall affect any subsequent event of default
or shall impair any rights or remedies consequent thereon.

      SECTION 8.04. RIGHT OF BONDHOLDERS TO DIRECT PROCEEDINGS. Anything in this
Indenture to the contrary notwithstanding, the Owners of not less than a
majority in aggregate principal amount of Bonds then outstanding shall have the
right, at any time, by an instrument or instruments in writing executed and
delivered to the Trustee, to direct the time, method and place of conducting all
proceedings to be taken in connection with the enforcement of the terms and
conditions of this Indenture, or for the appointment of a receiver or any other
proceedings hereunder; provided, that such direction shall not be otherwise than
in accordance with the provisions of law and of this Indenture.

      SECTION 8.05. APPLICATION OF MONEYS. All moneys received by the Trustee
pursuant to any right given or action taken under the provisions of this Article
shall, after payment of the costs and expenses of the proceedings resulting in
the collection of such moneys and of the fees, expenses, liabilities and
advances incurred or made by the Trustee and its Counsel, be deposited in the
Bond Fund and all such moneys and all other moneys then on deposit in the Bond
Fund (except as provided in Section 5.06 hereof and subject to the Tax
Agreement) shall be applied to the payment of the principal of, premium, if any,
and interest then due and unpaid upon the Bonds (except as provided in Section
5.06 hereof), without preference or priority of any kind, ratably, according to
the amounts due and payable on such Bonds for principal, premium, if any, and
interest, respectively, to the persons entitled thereto without any
discrimination or privilege.

      Whenever moneys are to be applied pursuant to the provisions of this
Section, such moneys shall be applied at such times, and from time to time, as
the Trustee shall determine. Whenever the Trustee shall apply such moneys, it
shall fix the date (which shall be an Interest Payment Date unless it shall deem
another date more suitable) upon which such application is to be made and upon
such date interest on the amounts of principal to be paid on such date shall
cease to accrue. The Trustee shall give such notice as it may deem appropriate
of the deposit with it of any such moneys and of the fixing of any such date.
Whenever all principal of, and premium, if any, and interest on, all Bonds have
been paid under the provisions of this Section 8.05 and all expenses and charges
of the Trustee have been paid, any balance remaining in the Bond Fund shall be
paid to the Company as provided in Section 5.09 hereof, subject to the
provisions of the Tax Agreement.

      SECTION 8.06. REMEDIES VESTED IN TRUSTEE. All rights of action (including
the right to file proofs of claims) under this Indenture or under any of the
Bonds may be enforced by the Trustee without the possession of any of the Bonds
or the production thereof in any trial or other proceedings relating thereto and
any such suit or proceeding instituted


                                      -32-
<PAGE>   37
by the Trustee shall be brought in its name as Trustee without the necessity of
joining as plaintiffs or defendants any Owners of the Bonds, and any recovery of
judgment shall be for the equal and ratable benefit of the Owners of the
outstanding Bonds.

      SECTION 8.07. RIGHTS AND REMEDIES OF BONDHOLDERS. No Owner of any Bond
shall have any right to institute any suit, action or proceeding in equity or at
law for the enforcement of this Indenture or for the execution of any trust
thereof or for the appointment of a receiver or any other remedy hereunder,
unless (i) a default has occurred of which the Trustee is deemed to have notice
or has been notified as provided in Section 9.0l(g) hereof, (ii) such default
shall have become an event of default and be continuing, (iii) the Owners of not
less than a majority in aggregate principal amount of Bonds then outstanding
shall have made written request to the Trustee, either to proceed to exercise
the powers herein granted or to institute such action, suit or proceeding in its
own name, and shall have offered to the Trustee indemnity as provided in Section
9.01(i), and (iv) the Trustee shall for sixty (60) days after such notice,
request and offer of indemnity fail or refuse to exercise the powers herein
granted, or to institute such action, suit or proceeding in its own name; and
such notification, request and offer of indemnity are hereby declared in every
case at the option of the Trustee to be conditions precedent to the execution of
the powers and trusts of this Indenture, and to any action or cause of action
for the enforcement of this Indenture, or for the appointment of a receiver or
for any other remedy hereunder. No one or more Owners of the Bonds shall have
any right in any manner whatsoever to enforce any right hereunder except in the
manner herein provided, and all proceedings at law or in equity shall be
instituted, had and maintained in the manner herein provided and for the equal
and ratable benefit of the Owners of all Bonds then outstanding. Nothing in this
Indenture contained shall, however, affect or impair the right of any Bondholder
to enforce the payment of the principal of, and premium, if any, and interest
on, any Bond at and after the maturity thereof.

      SECTION 8.08. TERMINATION OF PROCEEDINGS. In case the Trustee shall have
proceeded to enforce any right under this Indenture by the appointment of a
receiver or otherwise, and such proceedings shall have been discontinued or
abandoned for any reason, or shall have been determined adversely, then and in
every such case the Issuer, the Trustee and the Bondholders shall be restored to
their former positions and rights hereunder, respectively, and all rights,
remedies and powers of the Trustee shall continue as if no such proceedings had
been taken.

      SECTION 8.09. WAIVERS OF EVENTS OF DEFAULT. The Trustee may in its
discretion waive any event of default hereunder and rescind its consequences and
shall do so upon the written request of the Owners of not less than a majority
in aggregate principal amount of all Bonds then outstanding; provided, however,
that there shall not be waived any event of default in the payment of the
principal of, or premium on, any outstanding Bonds when due (whether at maturity
or by redemption), or any event of default in the payment when due of the
interest on any such Bonds, unless prior to such waiver and rescission, all
arrears of principal of and interest, with interest at the rate borne by the
Bonds on overdue principal and (to the extent permitted by law) on overdue
installments of interest, and all arrears of premium, if any, when due, together
with the reasonable fees and expenses of the Trustee


                                      -33-
<PAGE>   38
and of the holders of such Bonds, including reasonable attorneys' fees paid or
incurred, shall have been paid or provided for; provided further, that if the
Owners of not less than a majority in aggregate principal amount of the Bonds
then outstanding shall have made the written request specified in the first
paragraph of Section 8.02 hereof, then only upon receipt by the Trustee of the
express written consent of the Owners of a majority in principal amount of the
Bonds then outstanding (which consents the Trustee shall have no duty or
obligation to solicit). In the case of any such waiver and rescission, or in
case any proceeding taken by the Trustee on account of any such default shall
have been discontinued or abandoned or determined adversely, then and in every
such case the Issuer, the Trustee and the Bondholders shall be restored to their
former positions and rights hereunder, respectively, but no such waiver and
rescission shall extend to any subsequent or other default, or impair any right
consequent thereon. All waivers under this Indenture shall be in writing and a
copy thereof shall be delivered to the Issuer and to the Company.

      SECTION 8.10. OPPORTUNITY OF COMPANY TO CURE EVENTS OF DEFAULT. Anything
herein to the contrary notwithstanding, no default under Section 8.01(d) hereof
shall constitute an event of default until actual notice of such default by
registered or certified mail shall be given to the Issuer and the Company by the
Trustee or to the Issuer and the Company and the Trustee by the Owners of not
less than a majority in aggregate principal amount of all Bonds Outstanding, and
the Company shall have had sixty days after receipt of such notice to correct
said default or cause said default to be corrected, and shall not have corrected
said default or caused said default to be corrected within the applicable
period; provided, however, if said default be such that it cannot be corrected
within the applicable period, it shall not constitute an event of default if
corrective action is instituted within the applicable period and diligently
pursued until the default is corrected.

      Whenever, so long as the Company is not in default under the Agreement,
after a reasonable request by the Company, the Issuer shall fail, refuse or
neglect to give any direction to the Trustee or to require the Trustee to take
any other action which the Issuer is required to have the Trustee take pursuant
to the provisions of the Agreement or this Indenture, the Company instead of the
Issuer may give any such direction to the Trustee or require the Trustee to take
any such action. Upon receipt by the Trustee of a written notice signed by the
Authorized Company Representative stating that the Company has made reasonable
request of the Issuer, and that the Issuer has failed, refused or neglected to
give any direction to the Trustee or to require the Trustee to take any such
action (subject to indemnification which the Trustee deems adequate), the
Trustee is hereby irrevocably empowered and directed to accept such direction
from the Company as sufficient for all purposes of this Indenture. The Company
shall have the direct right to cause the Trustee to comply with any of the
Trustee's obligations under this Indenture to the same extent that the Issuer is
empowered so to do.

      Certain actions or failures to act by the Issuer under this Indenture may
create or result in an event of default under this Indenture and the Issuer
hereby grants the Company full authority, to the extent permitted by law, for
the account of the Issuer to perform or observe any covenant or obligation of
the Issuer alleged in a written notice to the Issuer and the Company from the
Trustee or from the requisite percentage of Owners of the Bonds not


                                      -34-
<PAGE>   39
to have been performed or observed, in the name and stead of the Issuer with
full power to do any and all things and acts to remedy any default.

                                   ARTICLE IX

                                   THE TRUSTEE

      SECTION 9.01. ACCEPTANCE OF THE TRUSTS. The Trustee hereby accepts the
trusts imposed upon it by this Indenture, represents and covenants that it is
fully empowered to accept said trusts, and agrees to perform said trusts, but
only upon and subject to the following express terms and conditions, and no
implied covenants or obligations shall be read into this Indenture against the
Trustee:

            (a) The Trustee may execute any of the trusts or powers hereof and
      perform any of its duties by or through attorneys, agents, receivers or
      employees and shall not be responsible for the acts of any attorneys,
      agents or receivers appointed by it in good faith and without negligence,
      shall not be responsible for the acts of any agents over which the Trustee
      has no control and has no power to appoint or remove and shall be entitled
      to advice of Counsel concerning all matters of trusts hereof and the
      duties hereunder, and may in all cases require that the Company pay such
      reasonable compensation to all such attorneys, agents and receivers as may
      reasonably be employed by the Trustee in connection with the trusts
      hereof. The Trustee may act upon the opinion or advice of Counsel. The
      Trustee shall not be responsible for any loss or damage resulting from any
      action or non-action in good faith in reliance upon such opinion or advice
      or any misconduct or negligence on the part of any agent or attorney
      appointed with due care.

            (b) Except for its certificate of authentication on the Bonds, the
      Trustee shall not be responsible for any recital herein or in the Bonds,
      or the validity, priority, recording, or re-recording, filing, or refiling
      of this Indenture or any financing statement, amendments to this
      Indenture, or continuation statements, or for reviewing any annual
      reports, financial statements or audits, or for insuring the Project or
      collecting any insurance moneys, or for the validity of the execution by
      the Issuer of this Indenture or for any supplements hereto or instruments
      of further assurance, or for the sufficiency of the security for the Bonds
      issued hereunder or intended to be secured hereby, for the value or title
      of the Project or as to the maintenance of the security hereof. The
      Trustee makes no representations as to the value or condition of the Trust
      Estate or any part thereof, or as to the title of the Issuer thereto or as
      to the security afforded thereby or hereby, or as to the validity or
      genuineness of any securities at any time pledged and deposited with the
      Trustee hereunder, or as to the validity or sufficiency of this Indenture
      or of the Bonds. The Trustee shall not be accountable for the use or
      application by the Company of the proceeds of the Bonds or of any money
      paid to the Company or upon the order of the Company under any provision
      hereof. The Trustee shall not be bound to ascertain or inquire as to the
      performance or observance of any covenants, conditions or agreements on
      the part of

                                      -35-
<PAGE>   40
      the Issuer or on the part of the Company under the Agreement, except as
      hereinafter set forth, but the Trustee may require of the Issuer or the
      Company full information and advice as to the performance of the
      covenants, conditions and agreements aforesaid. Except as otherwise
      provided in Sections 8.02 and 8.03 hereof, the Trustee shall have no
      obligation to perform any of the rights or duties of the Issuer under the
      Agreement. The Trustee shall not be responsible or liable for any loss
      suffered in connection with any investment of funds made by it in
      accordance with Article VI hereof including, without limitation, any loss
      suffered in connection with the sale of any investment pursuant to Article
      VI hereof.

            (c) The Trustee shall not be accountable for the use of any Bonds
      authenticated or delivered hereunder. The Trustee, in its individual
      capacity, may become the owner of Bonds with the same rights which it
      would have if it were not Trustee.

            (d) The Trustee shall be protected in acting in good faith upon any
      notice, request, resolution, consent, certificate, affidavit, letter,
      telegram, fax or other paper or document, or oral communication or
      direction, believed to be genuine and correct and to have been signed or
      sent or given by the proper person or persons. Any action taken by the
      Trustee pursuant to this Indenture upon the request or authority or
      consent of any person who at the time of making such request or giving
      such authority or consent is the owner of any Bond shall be conclusive and
      binding upon all future owners of the same Bond and upon Bonds issued in
      exchange therefor or upon transfer or in place thereof.

            (e) As to the existence or non-existence of any fact or as to the
      sufficiency or validity of any instrument, paper or proceeding, the
      Trustee shall be entitled to rely upon a certificate signed on behalf of
      the Issuer by an Authorized Issuer Representative as sufficient evidence
      of the facts therein contained, and prior to the occurrence of a default
      of which the Trustee has been notified as provided in subsection (g) of
      this Section, or subsequent to the waiver, rescission or annulment of a
      default as provided in Article VIII hereof, shall also be at liberty to
      accept a similar certificate to the effect that any particular dealing,
      transaction or action is necessary or expedient, but may at its discretion
      secure such further evidence deemed necessary or advisable, but shall in
      no case be bound to secure the same. The Trustee may accept a certificate
      signed on behalf of the Issuer by the Recording Officer to the effect that
      a resolution or ordinance in the form therein set forth has been adopted
      by the Issuer as conclusive evidence that such resolution or ordinance has
      been duly adopted, and is in full force and effect.

            (f) The permissive right of the Trustee to do things enumerated in
      this Indenture shall not be construed as a duty and the Trustee shall not
      be liable in the performance of its obligations hereunder except for its
      negligence or willful misconduct.


                                      -36-
<PAGE>   41
            (g) The Trustee shall not be required to take notice or be deemed to
      have notice of any default hereunder, except failure by the Issuer to
      cause to be made any of the payments to the Trustee required to be made by
      Article IV and all defaults under Section 8.01(a) or (b), unless the
      Trustee shall be specifically notified in writing of such default by the
      Issuer or the Owners of at least a majority in aggregate principal amount
      of all Bonds then affected or outstanding.

            (h) The Trustee shall not be required to give any bond or surety in
      respect of the execution of its trusts and powers hereunder.

            (i) Before taking any action under Article VIII hereof or this
      Section at the request or direction of the Bondholders, the Trustee may
      require that a satisfactory indemnity bond be furnished by the
      Bondholders, for the reimbursement of all expenses to which it may be put
      and to protect it against all liability, except liability which is
      adjudicated to have resulted from its negligence or willful misconduct in
      connection with any action so taken.

            (j) All moneys received by the Trustee shall, until used or applied
      as herein provided, be held in trust for the purposes for which they were
      received but need not be segregated from other funds except to the extent
      required by law or this Indenture. The Trustee shall not be under any
      liability for interest on any moneys received hereunder except such as may
      be agreed upon.

            (k) The Trustee, prior to the occurrence of an event of default
      specified in Section 8.0l of this Indenture of which it is deemed to have
      knowledge pursuant to clause (g) above and after the curing of all events
      of default which may have occurred, undertakes to perform such duties and
      only such duties as are specifically set forth in this Indenture and, in
      the absence of bad faith on its part, the Trustee may conclusively rely,
      as to the truth of the statements and correctness of the opinions
      expressed therein, upon certificates or opinions furnished to the Trustee
      and conforming to the requirements of this Indenture; but in the case of
      any such certificates or opinions which by any provision hereof are
      specifically required to be furnished to the Trustee, the Trustee shall be
      under a duty to examine the same to determine whether or not they conform
      to the requirements of this Indenture. In case an event of default has
      occurred (which has not been cured or waived) of which it is deemed to
      have knowledge pursuant to clause (g) above, the Trustee shall exercise
      such of the rights and powers vested in it by this Indenture, and use the
      same degree of care and skill in their exercise, as a prudent man would
      exercise or use under the circumstances in the conduct of his own affairs.

            (l) No provision of this Indenture shall be construed to relieve the
      Trustee from liability for its own negligent action, its own negligent
      failure to act, or its own willful misconduct, except that:

                  (i) This subsection shall not be construed to limit the effect
            of subsection (k) of this Section;


                                      -37-
<PAGE>   42
                 (ii) The Trustee shall not be liable for any error of judgment
            made in good faith by an officer of the Trustee unless it shall be
            proved that the Trustee was negligent in ascertaining the pertinent
            facts;

                (iii) The Trustee shall not be liable with respect to any action
            taken or omitted to be taken by it in good faith in accordance with
            the direction of the Owners of a majority in aggregate principal
            amount of the Bonds outstanding relating to the time, method and
            place of conducting any proceeding or any remedy available to the
            Trustee, or exercising any trust or power conferred upon the
            Trustee, under this Indenture; and

                 (iv) No provision of this Indenture shall require the Trustee
            to expend or risk its own funds or otherwise incur any financial
            liability in the performance of any of its duties hereunder, or in
            the exercise of any of its rights or powers, if it shall have
            reasonable grounds for believing that repayment of such funds or
            adequate indemnity against such risk or liability is not reasonably
            assured to it.

            (m) Notwithstanding anything elsewhere in this Indenture contained,
      the Trustee shall have the right, but shall not be required, to demand, in
      respect of the authentication of any Bonds, the withdrawal of any cash,
      the release of any property, or any action whatsoever within the purview
      of this Indenture, any showings, certificates, opinions, appraisals or
      other information, or corporate action or evidence thereof, in addition to
      that by the terms hereof required as a condition of such action by the
      Trustee, deemed desirable for the purpose of establishing the right of the
      Issuer to the authentication of any Bonds, the withdrawal of any cash, or
      as a condition to the taking of any action by the Trustee.

      SECTION 9.02. CORPORATE TRUSTEE REQUIRED; ELIGIBILITY. There shall at all
times be a Trustee hereunder which shall be a corporation organized and doing
business and authorized under such laws to exercise corporate trust powers,
authorized to accept and exercise the trusts herein provided, having a combined
capital and surplus of at least $50,000,000 and subject to supervision or
examination by federal or state authority. If such corporation publishes reports
of condition at least annually, pursuant to law or to the requirements of the
aforesaid supervising or examining authority, then for the purposes of this
Section 9.02, the combined capital and surplus of such corporation shall be
deemed to be its combined capital and surplus as set forth in its most recent
report of condition so published. If at any time the Trustee shall cease to be
eligible in accordance with the provisions of this Section, it shall resign
immediately in the manner and with the effect hereinafter specified in this
Article, and shall immediately provide notice of such resignation by registered
or certified mail to the Issuer, the Company and the Owner of each Bond.

      SECTION 9.03. FEES, CHARGES AND EXPENSES OF TRUSTEE. The Trustee shall be
entitled to payment and/or reimbursement from the Company for reasonable fees
for its Ordinary Services rendered hereunder and all advances, Counsel fees and
other Ordinary Expenses reasonably and necessarily made or incurred by the
Trustee in connection with


                                      -38-
<PAGE>   43
such Ordinary Services hereunder and under the Tax Agreement and, in the event
that it should become necessary that the Trustee perform Extraordinary Services,
it shall be entitled to reasonable extra compensation therefor from the Company,
and to reimbursement from the Company for reasonable and necessary Extraordinary
Expenses (including fees of Counsel) in connection therewith; provided, that if
such Extraordinary Services or Extraordinary Expenses are occasioned by the
neglect or misconduct of the Trustee it shall not be entitled to compensation or
reimbursement therefor. The Trustee shall be entitled to payment and
reimbursement from the Company for the reasonable fees and charges of the
Trustee as Bond Registrar and Paying Agent. Upon the occurrence and continuation
of an Event of Default hereunder, the Trustee shall have a first lien with right
of payment prior to payment on account of interest or principal of, or premium,
if any, on any Bond upon all moneys in its possession under any provisions
hereof for the foregoing advances, fees, costs and expenses incurred.

      SECTION 9.04. NOTICE TO BONDHOLDERS IF DEFAULT OCCURS. If a default occurs
of which the Trustee is by Section 9.01(g) hereof required to take notice or if
notice of default be given as in said Section 9.01(g) provided, the Trustee
shall, within fifteen (15) days thereafter (unless such default is cured or
waived), give notice of such default to each Owner of Bonds then outstanding,
provided that, except in the case of a default in the payment of the principal
of, or premium, if any, or interest on, any Bond, the Trustee may withhold such
notice to the Bondholders if and so long as the board of directors, the
executive committee, or a trust committee of directors and/or responsible
officers, of the Trustee in good faith determine that the withholding of such
notice is in the interests of the Bondholders.

      SECTION 9.05. INTERVENTION BY TRUSTEE. In any judicial proceeding to which
the Issuer is a party and which in the opinion of the Trustee and its counsel
has a substantial bearing on the interests of Owners of the Bonds, the Trustee
may intervene on behalf of Bondholders and, subject to the provisions of Section
9.01(i), shall do so if requested in writing by the Owners of a majority in
aggregate principal amount of all Bonds then outstanding.

      SECTION 9.06. SUCCESSOR TRUSTEE. Any corporation or association into which
the Trustee may be merged, or with which it may be consolidated, or to which it
may sell, lease or transfer its corporate trust business and assets as a whole
or substantially as a whole, shall be and become successor Trustee hereunder and
shall be vested with all the trusts, powers, rights, obligations, duties,
remedies, immunities and privileges hereunder as was its predecessor, without
the execution or filing of any instrument on the part of any of the parties
hereto.

      SECTION 9.07. RESIGNATION BY THE TRUSTEE. The Trustee may at any time
resign from the trusts hereby created by giving sixty (60) days written notice
by registered or certified mail to the Issuer, the Company and the Owner of each
Bond, and such resignation shall take effect at the appointment of a successor
Trustee pursuant to the provisions of Section 9.09 hereof and acceptance by the
successor Trustee of such trusts. If no successor Trustee shall have been so
appointed and have accepted appointment within forty-five (45)


                                      -39-
<PAGE>   44
days of the giving of written notice by the resigning Trustee as aforesaid, the
resigning Trustee may petition any court of competent jurisdiction for the
appointment of a successor Trustee.

      SECTION 9.08. REMOVAL OF THE TRUSTEE. The Trustee may be removed at any
time, by an instrument or concurrent instruments in writing delivered to the
Trustee, the Issuer and the Company and signed by the Owners of a majority in
aggregate principal amount of Bonds then Outstanding, or (so long as no event of
default is then existing under Section 6.1 of the Agreement or under Section
8.01 of this Indenture) by the Company by written instrument delivered to the
Trustee and the Issuer, and such removal shall only take effect at the
appointment of a successor Trustee pursuant to the provisions of Section 9.09
hereof and acceptance by the successor Trustee of such trusts.

      SECTION 9.09. APPOINTMENT OF SUCCESSOR TRUSTEE. In case the Trustee
hereunder shall:

            (a) resign pursuant to Section 9.02 or 9.07 hereof;

            (b) be removed pursuant to Section 9.08 hereof; or

            (c) be dissolved, taken under the control of any public officer or
      officers or of a receiver appointed by a court, or otherwise become
      incapable of acting hereunder,

a successor shall be appointed by the Issuer at the direction of the Company;
provided, that if a successor Trustee is not so appointed within ten (10) days
after notice of resignation is mailed or instrument of removal is delivered as
provided under Sections 9.02, 9.07 and 9.08 hereof, respectively, or within ten
(10) days of Issuer's knowledge of any of the events specified in (c)
hereinabove, then the Owners of a majority in aggregate principal amount of
Bonds then outstanding, by an instrument or concurrent instruments in writing
signed by or on behalf of such Owners, may designate a successor Trustee. Every
such successor Trustee appointed pursuant to the provisions of this Section
shall meet the requirements of Section 9.02 hereof and shall be a trust company
or bank in good standing, shall be eligible to serve as Trustee under the Act,
and willing to accept the trusteeship and all other terms and conditions
hereunder under the terms and conditions of this Indenture.

      In case at any time the Trustee shall resign and no appointment of a
successor Trustee shall be made pursuant to the foregoing provisions of this
Article IX prior to the date specified in the notice of resignation as the date
when such resignation shall take effect, the Owner of any Bond may apply to any
court of competent jurisdiction to appoint a successor Trustee. Such court may
thereupon, after such notice, if any, as it may deem proper and prescribe,
appoint a successor Trustee.

      SECTION 9.10. CONCERNING ANY SUCCESSOR TRUSTEES. Every successor Trustee
appointed hereunder shall execute, acknowledge and deliver to its predecessor
and also to the Issuer and the Company, an instrument in writing accepting such
appointment hereunder,


                                      -40-
<PAGE>   45
and thereupon such successor shall become fully vested with all the trusts,
powers, rights, obligations, duties, remedies, immunities and privileges of its
predecessor; but, nevertheless, (l) such predecessor shall, on the written
request of the Issuer at the direction of the Company, execute and deliver an
instrument transferring to such successor Trustee all the trusts, powers,
rights, obligations, duties, remedies, immunities and privileges of such
predecessor hereunder and (2) such predecessor shall deliver all securities and
moneys held by it as Trustee hereunder (net of any amounts owing to it
hereunder) to its successor. Should any instrument in writing from the Issuer be
required by any successor Trustee for more fully and certainly vesting in such
successor the trusts, powers, rights, obligations, duties, remedies, immunities
and privileges hereby vested in the predecessor any and all such instruments in
writing shall, on request, be executed, acknowledged and delivered by the Issuer
at the expense of the Company. The resignation of any Trustee and the instrument
or instruments removing any Trustee and appointing a successor hereunder,
together with all other instruments provided for in this Article, shall be filed
or recorded by the successor Trustee in each recording office, if any, where the
Indenture or a financing statement relating thereto shall have been filed or
recorded.

      SECTION 9.11. APPOINTMENT OF CO-TRUSTEE. It is the purpose of this
Indenture that there shall be no violation of any law of any jurisdiction
(including particularly the law of the State) denying or restricting the right
of banking corporations or associations to transact business as trustee in such
jurisdiction. It is recognized that in case of litigation under this Indenture
or the Agreement, and in particular in case of the enforcement thereof on
default, or in the case the Trustee deems that by reason of any present or
future law of any jurisdiction it may not exercise any of the powers, rights or
remedies herein granted to the Trustee or hold title to the properties, in
trust, as herein granted, or take any action which may be desirable or necessary
in connection therewith, it may be necessary that the Trustee appoint an
additional individual or institution as a separate or co-trustee. The following
provisions of this Section are adapted to these ends.

      In the event that the Trustee appoints an additional individual or
institution as a separate or co-trustee, each and every remedy, power, right,
claim, demand, cause of action, immunity, estate, title, interest and lien
expressed or intended by this Indenture to be exercised by or vested in or
conveyed to the Trustee with respect thereto shall be exercisable by and vest in
such separate or co-trustee but only to the extent necessary to enable such
separate or co-trustee to exercise such powers, rights and remedies, and only to
the extent that the Trustee by the laws of any jurisdiction (including
particularly the State) is incapable of exercising such powers, rights and
remedies and every covenant and obligation necessary to the exercise thereof by
such separate or co-trustee shall run to and be enforceable by either of them.

      Should any instrument in writing from the Issuer be required by the
separate or co-trustee so appointed by the Trustee for more fully and certainly
vesting in and confirming to him or it such properties, rights, powers, trusts,
duties and obligations, any and all such instruments in writing shall, on
request, be executed, acknowledged and delivered by the Issuer at the expense of
the Company; provided, that if an event of default shall have occurred and be
continuing, if the Issuer does not execute any such instrument within fifteen


                                      -41-
<PAGE>   46
(15) days after request therefor (which request shall contain notification of
such fifteen (15) day deadline), the Trustee shall be empowered as an
attorney-in-fact for the Issuer to execute any such instrument in the Issuer's
name and stead. In case any separate or co-trustee or a successor to either
shall die, become incapable of acting, resign or be removed, all the estates,
properties, rights, powers, trusts, duties and obligations of such separate or
co-trustee, so far as permitted by law, shall vest in and be exercised by the
Trustee until the appointment of a new trustee or successor to such separate or
co-trustee.

      The Trustee shall be entitled to remove any co-trustee so appointed by the
Trustee upon written notice to such co-trustee, the Issuer and the Company.

                                    ARTICLE X

                             SUPPLEMENTAL INDENTURES

      SECTION 10.01. SUPPLEMENTAL INDENTURES NOT REQUIRING CONSENT OF
BONDHOLDERS. The Issuer and the Trustee may without the consent of or notice to
any of the Bondholders enter into an indenture or indentures supplemental to
this Indenture for any one or more of the following purposes:

            A. to add to the covenants and agreements of, and limitations and
      restrictions upon, the Issuer in this Indenture other covenants,
      agreements, limitations and restrictions to be observed by the Issuer
      which are not contrary to or inconsistent with this Indenture as
      theretofore in effect;

            B. to grant to or confer or impose upon the Trustee for the benefit
      of the Bondholders any additional rights, remedies, powers, authority,
      security, liabilities or duties which may lawfully be granted, conferred
      or imposed and which are not contrary to or inconsistent with this
      Indenture as heretofore in effect;

            C. to cure any ambiguity or omission or to cure, correct or
      supplement any defective provision of this Indenture in each case in such
      manner as shall not adversely affect the Bondholders;

            D. to evidence the appointment of a separate Trustee or a co-trustee
      or to evidence the succession of a new Trustee hereunder;

            E. to comply with the requirements of the Trust Indenture Act of
      1939, as from time to time amended;

            F. to subject to this Indenture additional revenues, properties or
      collateral;

            G. to provide for the issuance of coupon bonds (provided, however,
      that the Issuer and the Trustee have received an opinion of Bond Counsel
      to the affect that issuance of such coupon bonds complies with the
      applicable laws and will not


                                      -42-
<PAGE>   47
      adversely affect the exclusion from gross income for federal income tax
      purposes of interest on any of the Bonds);

            H. to provide for the use or discontinuance of a book entry system;

            I. to maintain ratings on the Bonds;

            J. to preserve the exemption from Federal income taxes of interest
      on the Bonds, or any of them; or

             K. to modify, alter, amend or supplement this Indenture in any
      other respect which is not adverse to the Bondholders and which does not
      involve a change described in clauses (a), (b), (c) or (d) of the first
      paragraph of Section 10.02 hereof and which, in the judgment of the
      Trustee, is not to the prejudice of the Trustee.

      SECTION 10.02. SUPPLEMENTAL INDENTURES REQUIRING CONSENT OF BONDHOLDERS.
Exclusive of supplemental indentures covered by Section 10.01 hereof and subject
to the terms and provisions contained in this Section, and not otherwise, the
holders of not less than a majority in aggregate principal amount of the Bonds
then outstanding shall have the right, from time to time, anything contained in
this Indenture to the contrary notwithstanding, to consent to and approve the
execution by the Issuer and the Trustee of such other indenture or indentures
supplemental hereto for the purpose of modifying, amending, adding to or
rescinding, in any particular, any of the terms or provisions contained in this
Indenture; provided, however, that nothing in this Section contained shall
permit or be construed as permitting without the consent of the owners of 100%
in aggregate principal amount of the Bonds then outstanding (a) an extension of
the maturity date of the principal of or the interest on any Bond issued
hereunder, or (b) a reduction in the principal amount of, or premium, if any,
on, any Bond or the rate of interest thereon, or (c) a privilege or priority of
any Bond or Bonds over any other Bond or Bonds, or (d) a reduction in the
aggregate principal amount of the Bonds the owners of which are required to
consent to such supplemental indenture.

      If at any time the Issuer shall request the Trustee to enter into any such
supplemental indenture for any of the purposes allowed by this Section, the
Trustee shall, at the request of the Issuer and upon being satisfactorily
indemnified with respect to expenses, cause notice of the proposed execution of
such supplemental indenture to be mailed in substantially the manner provided in
the first paragraph of Section 3.04 hereof with respect to redemption of Bonds.
Such notice shall briefly set forth the nature of the proposed supplemental
indenture and shall state that copies thereof are on file at the Corporate Trust
Office of the Trustee for inspection by all Bondholders. If, within sixty (60)
days or such longer period of time as shall be prescribed by the Issuer
following the mailing of such notice, the Owners of not less than a majority or
100%, as the case may be, in aggregate principal amount of the Bonds outstanding
at the time of the execution of any such supplemental indenture shall have
consented to and approved the execution thereof as herein provided, no Owner of
any Bond shall have any right to object to any of the terms and provisions
contained therein, or the operation thereof, or in any manner to question the
propriety of the execution thereof, or to


                                      -43-
<PAGE>   48
enjoin or restrain the Trustee or the Issuer from executing the same or from
taking any action pursuant to the provisions thereof. The Issuer shall have the
right to extend from time to time the period within which such consent and
approval may be obtained from Bondholders. Upon the execution of any such
supplemental indenture as in this Section permitted and provided, this Indenture
shall be and be deemed to be modified and amended in accordance therewith.

      SECTION 10.03. CONSENTS TO SUPPLEMENTAL INDENTURES. Anything herein to the
contrary notwithstanding, a supplemental indenture under this Article X which
affects any rights or obligations of the Company shall not become effective
unless and until the Company shall have consented to the execution and delivery
of such supplemental indenture. The Company shall be given prior written notice
of the proposed execution and delivery of any supplemental indenture whether or
not its rights or obligations are affected. In this regard, the Trustee shall
cause notice of the proposed execution and delivery of any such supplemental
indenture together with a copy of the proposed supplemental indenture to be
mailed by certified or registered mail to the Company at least fifteen (15) days
prior to the date of the first mailing of notice of the proposed execution of
such supplemental indenture as hereinbefore in Section 10.02 provided. The
Company shall be deemed to have consented to the execution and delivery of any
such supplemental indenture if the Trustee does not receive at its principal
corporate trust office a letter of protest or objection thereto signed by or on
behalf of the Company on or before 4:30 o'clock P.M., New York time, of the
fifteenth day after the mailing of said notice and a copy of the proposed
supplemental indenture.

      SECTION 10.04. RELIANCE ON OPINIONS OF COUNSEL. The Issuer and the Trustee
may rely on an opinion of Counsel to the effect that any supplemental indenture
entered into by the Issuer and the Trustee complies with the provisions of this
Article X and an opinion of Bond Counsel that any such supplemental indenture
does not adversely affect the exclusion from federal gross income of interest on
the Bonds.

                                   ARTICLE XI

                             AMENDMENT OF AGREEMENT

      SECTION 11.01. AMENDMENTS, ETC., TO AGREEMENT NOT REQUIRING CONSENT OF
BONDHOLDERS. The Issuer and the Company may, with the written consent of the
Trustee, but without the consent of or notice to any of the Bondholders, enter
into any amendment, change or modification of the Agreement (a) as may be
required by the provisions of the Agreement or this Indenture, (b) for the
purpose of curing any ambiguity or formal defect or omission in the Agreement,
(c) to preserve the exemption from Federal income taxes of interest on the
Bonds, or any of them, (d) to change Exhibit A to the Agreement in accordance
with the provisions of the Agreement or the Project Certificate or (e) in
connection with any other change therein which is not to the prejudice of the
Trustee or the Owners of the Bonds.


                                      -44-
<PAGE>   49
      SECTION 11.02. AMENDMENTS, ETC., TO AGREEMENT REQUIRING CONSENT OF
BONDHOLDERS. Except for the amendments, changes or modifications as provided in
Section 11.01 hereof, the Issuer and the Company shall not enter into, and the
Trustee shall not consent to, any other amendment, change or modification of the
Agreement without mailing of notice to, and the written approval or consent of,
the Owners of not less than a majority in aggregate principal amount of the
Bonds at the time outstanding given and procured as provided in this Section;
provided, however, that nothing in this Section or Section 11.01 hereof shall
permit or be construed as permitting without the consent of the owners of 100%
in aggregate principal amount of the Bonds then outstanding (a) an extension of
the time of the payment of any amounts payable under Section 4.2(a) of the
Agreement, or (b) a reduction in the amount of any payment or in the total
amount due under Section 4.2(a) of the Agreement or (c) a reduction in the
aggregate principal amount of the Bonds required for consent to an amendment of
the Agreement. If at any time the Issuer and the Company shall request the
consent of the Trustee to any such proposed amendment, change or modification of
the Agreement, the Trustee shall, at the request of the Issuer and upon being
satisfactorily indemnified with respect to expenses, cause notice of such
proposed amendment, change or modification to be mailed to the Owners of Bonds
in the same manner as provided by the first paragraph of Section 3.04 hereof
with respect to redemption of Bonds. Such notice shall briefly set forth the
notice of such proposed amendment, change or modification and shall state that
copies of the instrument embodying the same are on file with the Trustee for
inspection by all Bondholders. If, within sixty (60) days, or such longer period
as shall be prescribed by the Issuer in its reasonable judgment, following the
mailing of such notice, the Owners of not less than a majority or 100%, as the
case may be, in aggregate principal amount of the Bonds outstanding at the time
of the execution of any such amendment, change or modification shall have
consented to and approved the execution thereof as herein provided, no Owner of
any Bond shall have any right to object to any of the terms and provisions
contained therein, or the operation thereof, or in any manner to question the
propriety of the execution thereof, or to enjoin or restrain the Company or the
Issuer from executing the same or from taking any action pursuant to the
provisions thereof, or the Trustee from consenting thereto. The Issuer shall
have the right to extend from time to time the period within which such consent
and approval may be obtained from Bondholders. Upon the execution of any such
amendment, change or modification as in this Section permitted and provided, the
Agreement shall be and be deemed to be modified, changed and amended in
accordance therewith.

      SECTION 11.03. RELIANCE ON OPINIONS OF COUNSEL. The Issuer and the Trustee
may rely upon an opinion of Counsel to the effect that any proposed amendment,
change or modification to the Agreement will comply with the provisions of this
Article XI and an opinion of Bond Counsel that any such amendment, change or
modification does not adversely affect the exclusion from federal gross income
of interest on the Bonds.


                                      -45-
<PAGE>   50
                                   ARTICLE XII

                                  MISCELLANEOUS

      SECTION 12.01. CONSENTS, ETC., OF BONDHOLDERS. Any consent, approval,
direction or other instrument required by this Indenture to be signed and
executed by the Bondholders may be in any number of concurrent writings of
similar tenor and may be signed or executed by such Bondholders in person or by
agent appointed in writing. Proof of the execution of any such consent,
approval, direction or other instrument or of the writing appointing any such
agent, if made in the following manner, shall be sufficient for any of the
purposes of this Indenture, and shall be conclusive in favor of the Trustee with
regard to any action taken under such request or other instrument, namely:

            (a) The fact and date of the execution by any Person of any such
      instrument or writing may be proved by the certificate of any officer in
      any jurisdiction who by law has power to take acknowledgments within such
      jurisdiction that the Person signing such instrument or writing
      acknowledged before him the execution thereof, or by affidavit of any
      witness to such execution or in any other manner satisfactory to the
      Trustee;

            (b) The fact of ownership of Bonds and the amount or amounts,
      numbers and other identification of such Bonds, and the date of acquiring
      the same shall be proved by the registration books of the Issuer
      maintained by the Trustee pursuant to Section 2.03 hereof.

      SECTION 12.02. LIMITATION OF RIGHTS. With the exception of rights herein
expressly conferred, nothing expressed or mentioned in or to be implied from
this Indenture or the Bonds is intended or shall be construed to give to any
person other than the parties hereto, the Company and the Owners of the Bonds
any legal or equitable right, remedy or claim under or in respect to this
Indenture. This Indenture and all of the covenants, conditions and provisions
hereof are intended to be and being for the sole and exclusive benefit of the
parties hereto, the Owners of the Bonds and the Company as herein provided.

      SECTION 12.03. SEVERABILITY. If any provision of this Indenture shall be
invalid, inoperative or unenforceable as applied in any particular case in any
jurisdiction or jurisdictions or in all jurisdictions, or in all cases because
it conflicts with any other provision or provisions hereof or any constitution
or statute or rule of public policy, or for any other reason, such circumstances
shall not have the effect of rendering the provision in question inoperative or
unenforceable in any other case or circumstance, or of rendering any other
provision or provisions herein contained invalid, inoperative, or unenforceable
to any extent whatever. The invalidity of any one or more phrases, sentences,
clauses or Sections in this Indenture contained, shall not affect the remaining
portions of this Indenture, or any part thereof.

      SECTION 12.04. NOTICES. Except as otherwise expressly provided herein, all
notices, certificates or other communications hereunder shall be sufficiently
given and shall be


                                      -46-
<PAGE>   51
deemed given on the day on which the same have been mailed by first class mail
postage prepaid, or delivered by hand, or sent by telecopy or similar facsimile
transmission, as follows: if to the Issuer, c/o Lewis and Roca, LLP., 40 North
Central Avenue, Phoenix, Arizona 85004-4429, or to telecopy number (602)
262-5311; if to the Company, at 4000 East Sky Harbor Boulevard, Phoenix, Arizona
85034, or to telecopy number (602) 693-8953, Attention: Treasurer; if to the
Trustee, at 3300 North Central Avenue, 15th Floor, Phoenix, Arizona 85012,
Attention: Corporate Trust Services; provided, however, that notice to the
Trustee shall be deemed given when received by the Trustee. A duplicate copy of
each notice, certificate or other communication given hereunder by either the
Issuer or the Trustee to the other shall also be given to the Company. The
Issuer, the Company and the Trustee may, by notice given hereunder, designate
any further or different addresses to which subsequent notices, certificates or
other communications shall be sent.

      SECTION 12.05. HOLIDAYS. Except as otherwise expressly set forth herein,
if the date for making any payment or the last date for performance of any act
or the exercising of any right, as provided in this Indenture, is not a Business
Day, such payment may be made or act performed or right exercised on the next
succeeding Business Day with the same force and effect as if done on the nominal
date provided in this Indenture.

      SECTION 12.06. COUNTERPARTS. This Indenture may be simultaneously executed
in several counterparts, each of which shall be an original and all of which
shall constitute but one and the same instrument.

      SECTION 12.07. APPLICABLE LAW. The power and authority of the Issuer to
issue the Bonds and the rights and obligations of the Issuer hereunder shall be
governed by and construed in accordance with the laws of the State, except that
the Trustee's rights, duties, immunities and its standard of care in the
performance of its responsibilities under this Indenture shall be governed by
and construed in accordance with the laws of the state in which is located the
Trustee's Corporate Trust Office.

      SECTION 12.08. CAPTIONS. The captions or headings in this Indenture are
for convenience only and in no way define, limit, or describe the scope or
intent of any provisions or sections of this Indenture.

      SECTION 12.09. NOTICE REGARDING CANCELLATION OF CONTRACTS. As required by
the provisions of Section 38-511, Arizona Revised Statutes, as amended, notice
is hereby given that political subdivisions of the State of Arizona or any of
their departments or agencies may, within three (3) years of its execution,
cancel any contract, without penalty or further obligation, made by the
political subdivisions or any of their departments or agencies on or after
September 30, 1988, if any person significantly involved in initiating,
negotiating, securing, drafting or creating the contract on behalf of the
political subdivisions or any of their departments or agencies is, at any time
while the contract or any extension of the contract is in effect, an employee or
agent of any other party to the contract in any capacity or a consultant to any
other party of the contract with respect to the subject matter of the contract.
The cancellation shall be effective when written notice from the chief


                                      -47-
<PAGE>   52
executive officer or governing body of the political subdivision is received by
all other parties to the contract unless the notice specifies a later time.

      The Trustee covenants and agrees not to employ as an employee, agent or,
with respect to the subject matter of the Indenture, a consultant, any person
significantly involved in initiating, negotiating, securing, drafting or
creating this Indenture on behalf of the Issuer within three (3) years from the
execution hereof, unless a waiver is provided by the Issuer.

      IN WITNESS WHEREOF, THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF
PHOENIX, Arizona, has caused these presents to be signed in its name and behalf
by its President and its corporate seal to be hereunto affixed and attested by
its Secretary, and to evidence its acceptance of the trusts hereby created
Norwest Bank Arizona, N.A. has caused these presents to be signed in its name
and behalf as of the first day of April, 1998.

                                       THE INDUSTRIAL DEVELOPMENT AUTHORITY OF
                                           THE CITY OF PHOENIX, ARIZONA


                                       By 
                                          -------------------------------------
                                          President

Attest:


----------------------------------
Assistant Secretary


                                       NORWEST BANK ARIZONA, N.A., as Trustee


                                       By /s/ illegible
                                          -------------------------------------
                                          Its Assistant Vice President


                                      -48-
<PAGE>   53
     IN WITNESS WHEREOF, THE INDUSTRIAL DEVELOPMENT AUTHORITY OF THE CITY OF
PHOENIX, ARIZONA, has caused these presents to be signed in its name and behalf
by its President and its corporate seal to be hereunto affixed and attested by
its Secretary, and to evidence its acceptance of the trusts hereby created
Norwest Bank Arizona, N.A. has caused these presents to be signed in its name
and behalf by one of its                     and its official seal to be
hereunto affixed, and the same to be attested by one of its              , all
as of the first day of April, 1998.

                                         THE INDUSTRIAL DEVELOPMENT AUTHORITY
                                           OF THE CITY OF PHOENIX, ARIZONA


                                         By  /s/ illegible 
                                             ----------------------------------
                                             President


Attest:

/s/ illegible
----------------------------------
Assistant Secretary


                                         NORWEST BANK ARIZONA, N.A., as Trustee


                                         By 
                                            -----------------------------------
                                            Its 
                                               --------------------------------


(SEAL)

Attest:


----------------------------------
Its
    ------------------------------



                                      -49-

<PAGE>   54
                                    EXHIBIT I


                                 INVESTOR LETTER
                                  April 2, 1998


City of Phoenix
Phoenix, Arizona

The Industrial Development Authority
of the City of Phoenix, Arizona



      Re:             THE INDUSTRIAL DEVELOPMENT AUTHORITY
                         OF THE CITY OF PHOENIX, ARIZONA
                       AIRPORT FACILITIES REFUNDING BONDS
                      (AMERICA WEST AIRLINES, INC. PROJECT)
                                   SERIES 1998

Ladies and Gentlemen:

      The undersigned, [insert name of purchaser] (the "Purchaser"), has
purchased $29,300,000 principal amount of the Bonds. In connection with such
purchase, The Industrial Development Authority of the City of Phoenix, Arizona
(the "Issuer") and the City of Phoenix, Arizona (the "City") require that the
Purchaser make certain representations as to the Purchaser's willingness to
accept the risks of investing in the Bonds, the Purchaser's investigation of
such risks, and such other matters. Accordingly, the Purchaser represents and
warrants to the Issuer, the City, and other addressees hereof as follows:

       A. QUALIFICATION. The Purchaser is either a "qualified institutional
buyer" (a "Qualified Institutional Buyer") within the meaning of Rule 144A of
the Securities Act of 1933 (the "Securities Act") or a non-natural "accredited
investor" as defined in Rule 501 of Regulation D of the United States Securities
and Exchange Commission (an "Accredited Investor"). The Purchaser can bear the
economic risk of the purchase of the Bonds and has such knowledge and experience
in business and financial matters, including the analysis of the purchase of
similar investments, as to be capable of evaluating the merits and risks of an
investment in the Bonds on the basis of the information requested and reviewed
by us and our review as described herein.

       B. NO REGISTRATION; TRANSFERABILITY. The Purchaser acknowledges that the
Bonds are not currently required to be, have not been, and are not intended to
be, registered under the Securities Act or registered or otherwise qualified
under the securities laws of any


                                    EXHIBIT I
<PAGE>   55
state or other jurisdiction, and that any sale or other transfer of the Bonds
may be only in accordance with such laws. The Bonds are rated "____" by Moody's
Investors Service, Inc., and their transferability is limited to Qualified
Institutional Buyers or Accredited Investors.

       C. INDEPENDENT EVALUATION; WAIVER OF ISSUER'S DUE DILIGENCE; RELEASE. The
Purchaser has independently evaluated the factors associated with its investment
decision. The Purchaser has been given full and complete access to and has been
furnished with all information requested by the Purchaser regarding the Company,
and has conducted such other investigations relating to the Issuer, the Company,
the Project, and the Bonds, as in the opinion of the Purchaser was necessary in
connection with its purchase of the Bonds. The Purchaser acknowledges that the
Issuer, the members of its Board of Directors, its officers, Quarles & Brady,
its counsel and Villanueva & Company, its financial advisor and the City and its
City Council and agents of any of the foregoing (each individually an "Issuer
Party" and all collectively the "Issuer Parties") have not undertaken to furnish
information to the Purchaser, or to ascertain the accuracy or completeness of
any information that may have been furnished to the Purchaser by or on behalf of
the Issuer or the Company relating to the operations, financial conditions or
future prospects of the Company or the Project and that none of the Issuer
Parties have made any representations concerning the accuracy or completeness of
any information supplied to the Purchaser or relating to the Company and the
Project. The Purchaser hereby waives any requirements of due diligence in
investigation or inquiry on the part of any of the Issuer Parties and all
claims, actions, or causes of action which the Purchaser may have directly or
indirectly from or relating to any action which the Issuer and its Board of
Directors or the City and its City Council took, or could have taken, in
connection with the issuance and sale of the Bonds to the Purchaser.

       D. DISCLOSURE STATEMENT. We have carefully read the Limited Offering
Memorandum relating to the Bonds in its entirety and understand the risks
described therein and understand and acknowledge that there may be other risks
in such investment which are not described therein. We acknowledge that the
Bonds are a speculative investment and that there is a high degree of risk in
such investment.

       E. SOPHISTICATION. The Purchaser is sufficiently knowledgeable and
experienced in financial and business matters, including the purchase and
ownership of municipal and other tax-exempt obligations, to be able to evaluate
the risks and merits of the investment represented by the purchase of the Bonds,
and is capable of and has made its own investigation of the Borrower and the
Project in connection with its decision to purchase the Bonds.

       F. LEGAL AUTHORIZATION. The Purchaser is duly and legally authorized to
purchase the Bonds, and the Purchaser is duly and legally authorized to execute
this Investor Letter. The Purchaser has satisfied itself that the Bonds are a
lawful investment for it under all applicable laws.

       F. SPECIAL LIMITED OBLIGATIONS. The Purchaser understand that the Bonds
are special limited, and not general obligations of the Issuer payable solely
from the revenues received by Norwest Bank Arizona, National Association, as
trustee (the "Trustee"). The


                                      I-2
<PAGE>   56
Purchaser understands that the Bonds are not secured by any obligations or the
pledge of any monies received or to be received from taxation or from the State
of Arizona (the "State") or any political subdivision or taxing district thereof
(including, without implied limitation, the Issuer or the City), and that the
Bonds will never represent or constitute a general obligation, debt, or bonded
indebtedness of the City, the State, or any political subdivision thereof, and
that no right will exist to have taxes levied by the City, the State, or any
political subdivision thereof, for the payment of the principal of, premium, if
any, and interest on the Bonds, and that payment of the principal of, premium,
if any, and interest on the Bonds depends upon the general credit of the
Company. The Purchaser understands that the Issuer has no taxing power.

       H. SURVIVAL. All representations of the Purchaser contained herein shall
survive the sale and delivery of the Bonds to the Purchaser as representations
of fact existing as of the date of execution and delivery of this Investor
Letter.

       I. DEFINED TERMS. The initial capitalized terms not defined herein shall
the meaning ascribed to such terms in the Indenture of Trust which secures the
payment of the Bonds.

      J. WAIVER OF DUE DILIGENCE. Notwithstanding anything to the contrary
herein, the Purchaser waives any requirement of due diligence and investigation
or inquiry on the part of any of the Issuer Parties.

      The above representations are provided solely for the benefit of the
addressees of this Investor Letter and may not be relied upon by or furnished to
any other person without our prior written consent.

                                  ______________________________



                                  By __________________________________________
                                     
                                     __________________________________________
                                  
                                   Its ________________________________________
                                       
                                  [Note:  The signatory must be Chief Financial
                                     Officer or other executive officer.]


                                      I-3