41 C.F.R. § 301-10.141
Certification requirements for foreign air carrier use
Employees must provide a certification as required in this section and any additional documents specified by the agency. The agency will not pay the foreign air carrier fare without the required certification. The certification must include—
(a) Employee's name;
(b) Travel dates;
(c) Origin and destination;
(d) Detailed travel itinerary, including air carrier and flight number for each leg of the trip; and
(e) Statement explaining compliance with exceptions in § 301-10.134 or § 301-10.136, or a copy of the agency's written approval deeming foreign air carrier service necessary in accordance with § 301-10.135.