**TRUST
INDENTURE AND MORTGAGE 646 SUPPLEMENT**
 
 This
TRUST INDENTURE AND MORTGAGE 646 SUPPLEMENT NO. 1, dated December 1, 1997
(herein called this “Trust Indenture Supplement”) of FIRST SECURITY, NATIONAL
ASSOCIATION, not in its individual capacity, but solely as Owner Trustee (herein
called the “Owner Trustee”) under that certain Trust Agreement 646 dated as of
November 21, 1997 (the “Trust Agreement”), between the Owner Trustee and the
Owner Participant named therein.
 
 **W
I T N E S S E T H:**
 
 WHEREAS,
the Trust Indenture and Mortgage 646, dated as of November 21, 1997 (as amended
and supplemented to the date hereof, the “Trust Indenture”) between the Owner
Trustee and Wilmington Trust Company, as Mortgage (the “Mortgagee”), provides
for the execution and delivery of a supplement thereof substantially in the form
hereof, which shall particularly describe the Aircraft, and shall specifically
mortgage such Aircraft to the Mortgagee; and
 
 WHEREAS,
each of the Trust Agreement and Trust Indenture relates to the Airframe and
Engines described below, and or counterpart of the Trust Indenture is attached
hereto and made a part hereof and this Trust Indenture Supplement, together with
such counterpart of the Trust Indenture, is being filed for recordation on the
date hereof with the FAA as on document;
 
 NOW,
THEREFORE, this Trust Indenture Supplement witnesseth that the Owner Trustee
hereby confirms that the Lien of the Trust Indenture on the Trust Indenture
Estate covers all of Owner Trustee’s right, title and interest in and to the
following described property:
 
 **AIRFRAME**
 
 One
airframe identified as follows:
 
 FAARegistration
    Manufacturer’sManufacturer
    Model
    Number
    Serial
      NumberThe
      Boeing Company
    737-524
    N16646
    28907
 
 together
with all of the Owner Trustee’s right, title and interest in and to all Parts of
whatever nature, whether now owned or hereinafter acquired and which are from
time to time incorporated or installed in or attached to said
airframe.
 
 
 
 
 **AIRCRAFT
ENGINES**
 
 Two
aircraft engines, each such having 750 or more rated take-off horsepower or the
equivalent thereof, identifies as follows:
 
 Manufacturer   Manufacturer’s
Model   Serial
Number
 
 CFM
International, Inc.   56-3B-1    858732
 
 CFM
International, Inc.   56-3B-1    858696
 
 together
with all of Owner Trustee’s right, title and interest in and to all Parts of
whatever nature, whether now owned or hereafter acquired and which are from time
to time incorporated or installed in or attached to either of such
engines.
 
 Together
with all of Owner Trustee’s right, title and interest in and to (a) all Parts of
whatever nature, which from time to time are included within the definition of
“Airframe” or “Engine”, whether now owned or hereafter acquired, including all
substitutions, renewals and replacements of and additions, improvements,
accessions and accumulations to the Airframe and Engines (other than additions,
improvements, accession and accumulation which constitute appliances, parts,
instruments, appurtenances, accessories, furnishings or other equipment excluded
from the definition of Parts) and (b) all Aircraft Documents.
 
 As
further security for the obligations referred to above and secured by the Trust
Indenture and hereby, the Owner Trustee has granted, bargained, sold, assigned,
transferred, conveyed, mortgaged, pledged and confirmed, and does hereby grant,
bargain, sell, assign, transfer, convey, mortgage, pledge and confirm, unto the
Mortgagee, its successors and assigns, for the security and benefit of the Loan
Participants, the Note Holders and the Indenture Indemnitees, in the trust
created by the Trust Indenture, all the right, title and interest of the Owner
Trustee in, to and under the Lease Supplement of even date herewith covering the
property described above.
 
 Notwithstanding
any provision hereof, no Excluded Payment shall constitute security for any of
the aforementioned obligations.
 
 TO HAVE
AND TO HOLD all and singular the aforesaid property unto the Mortgagee, its
successors and assigns, in trust for the equal and proportionate benefit and
security of the Loan Participants the Note Holders and the Indenture
Indemnitees, except as provided in Section 2.14 and Article III of the Trust
Indenture without any preference, distinction or priority of any one Equipment
Note over any other by reason of priority of time of issue, sale, negotiation,
date of maturity thereof or otherwise for any reason whatsoever, and for the
uses and purposes and subject to the terms and provisions set forth in the Trust
Indenture.
 
 This
Trust Supplement shall be construed as supplemental to the Trust Indenture and
shall form a part thereof. The Trust Indenture is each hereby incorporated by
reference herein and is hereby ratified, approved and confirmed.
 
 AND,
FURTHER, the Owner Trustee hereby acknowledges that the Aircraft referred to in
this Trust Indenture Supplement and the aforesaid Lease Supplement has been
delivered to the Owner Trustee and is included in the property of the Owner
Trustee covered by all the terms and conditions of the Trust Agreement, subject
to the pledge and mortgage thereof under the Trust Indenture.
 
 
 [This
space intentionally left blank]
  
  
 
 IN
WITNESS WHEREOF, the Owner Trustee has caused this Trust Indenture Supplement to
be duly executed by one of its officers, thereunto duly authorized, on the day
and year first above written
 
 FIRST
SECURITY BANK, NATIONAL
 ASSOCIATION,
not in its individual capacity, except as expressly provided herein but solely
as Owner Trustee, Owner Trustee
 
 By:____________________________________
 Name:
 Title:
  
  
 
 TRUST
INDENTURE AND MORTGAGE
 
 Schedule
I
  Original Amount  Interest
Rate
 
 Series
A:   $11,451,300.00 7.461%
 
 Series
B:   $3,885,643.86 7.461%
 
 Series
C:   $3,063,056.14 7.420%
  
  
 TRUST
INDENTURE AND MORTGAGE
 Series
A
 
 Equipment
Note Amortization
  Percentage
      ofOriginal
      AmountPayment
      Date
    to
      be PaidApr
      1 1998
    2.50000017Oct
      1 1998
    -Apr
      1 1999
    2.50000000Oct
      1 1999
    -Apr
      1 2000
    2.50000000Oct
      1 2000
    -Apr
      1 2001
    5.01779711Oct
      1 2001
    -Apr
      1 2002
    11.55245003Oct
      1 2002
    -Apr
      1 2003
    1.12420092Oct
      1 2003
    -Apr
      1 2004
    -Oct
      1 2004
    -Apr
      1 2005
    -Oct
      1 2005
    -Apr
      1 2006
    -Oct
      1 2006
    -Apr
      1 2007
    5.96623484Oct
      1 2007
    -Apr
      1 2008
    6.07907879Oct
      1 2008
    -Apr
      1 2009
    -Oct
      1 2009
    -Apr
      1 2010
    -Oct
      1 2010
    -Apr
      1 2011
    5.02759591Oct
      1 2011
    -Apr
      1 2012
    12.90784321Oct
      1 2012
    -Apr
      1 2013
    17.53050614Oct
      1 2013
    -Apr
      1 2014
    18.01133129Oct
      1 2014
    -Apr
      1 2015
    9.28296159
 
  TRUST
INDENTURE AND MORTGAGE
 Series
B
 
 Equipment
Note Amortization
  Percentage
      ofOriginal
      AmountPayment
      Date
    to
      be PaidApr
      1 1998
    1.88382833Oct
      1 1998
    -Apr
      1 1999
    4.37317491Oct
      1 1999
    -Apr
      1 2000
    6.98048791Oct
      1 2000
    -Apr
      1 2001
    0.67234161Oct
      1 2001
    -Apr
      1 2002
    -Oct
      1 2002
    -Apr
      1 2003
    -Oct
      1 2003
    -Apr
      1 2004
    -Oct
      1 2004
    -Apr
      1 2005
    -Oct
      1 2005
    -Apr
      1 2006
    12.59606921Oct
      1 2006
    -Apr
      1 2007
    -Oct
      1 2007
    -Apr
      1 2008
    -Oct
      1 2008
    -Apr
      1 2009
    24.59386873Oct
      1 2009
    -Apr
      1 2010
    31.06637493Oct
      1 2010
    -Apr
      1 2011
    17.83385437
 
  TRUST
INDENTURE AND MORTGAGE
 Series
C
 
 Equipment
Note Amortization
 Percentage
      ofOriginal
      AmountPayment
      Date
    to
      be PaidApr
      1 1998
    -Oct
      1 1998
    -Apr
      1 1999
    -Oct
      1 1999
    -Apr
      1 2000
    -Oct
      1 2000
    -Apr
      1 2001
    -Oct
      1 2001
    -Apr
      1 2002
    -Oct
      1 2002
    -Apr
      1 2003
    34.83275759Oct
      1 2003
    -Apr
      1 2004
    33.55579046Oct
      1 2004
    -Apr
      1 2005
    29.50125818Oct
      1 2005
    -Apr
      1 2006
    2.11019377