We have performed the procedures contained in this report, which we agreed to perform and with which the Inspector General (IG) of the Department of Transportation concurred, solely to assist that office in ascertaining whether the net excise tax revenue distributed to the Airport and Airway Trust Fund (AATF) for the fiscal year ended September 30, 2004, is supported by the underlying records. We evaluated fiscal year 2004 activity affecting distributions to the AATF. The adequacy of the procedures to meet the IG's objectives is the IG's responsibility, and we make no representation in that respect. The procedures we agreed to perform were (1) detailed tests of transactions that represent the underlying basis of amounts distributed to the AATF, (2) review of the Internal Revenue Service's (IRS) quarterly AATF certifications, (3) review of the Department of the Treasury's Financial Management Service adjustments to the AATF for fiscal year 2004, (4) review of IRS's precertification1 of receipts for the second and third quarters of fiscal year 2004, (5) review of certain procedures of the Department of the Treasury's Office of Tax Analysis' (OTA) estimation procedures affecting excise tax distributions to the AATF for the fourth quarter of fiscal year 2004, and other procedures including (6) compiling and reporting the net amount of fiscal year 2004 excise taxes distributed to the AATF, (7) detailed tests of transactions that represent total IRS tax revenue receipts and refunds, and (8) review of key reconciliations of IRS records to Treasury records.