14 CFR 249.31: Preservation and inspection of evidence of compliance.

Air carriers and foreign air carriers shall preserve evidence of compliance with the requirements imposed under Regulation Z of the Board of Governors of the Federal Reserve System (12 CFR part 226), implementing the provisions of Title I (Truth in Lending) and Title V (General Provisions) of the Consumer Credit Protection Act, as amended (15 U.S.C. 1601 et seq.) other than the advertising requirements under § 226.10 of regulation Z. This evidence shall be preserved for no less than 2 years after the date each disclosure is required to be made and shall be made available for inspection by authorized representatives of the DOT.