Section 301-10.138 - In what circumstances is foreign air carrier service deemed a matter of necessity?(a) Foreign air carrier service is deemed a necessity when service by a U.S. flag air carrier is available, but(1) Cannot provide the air transportation needed; or(2) Will not accomplish the agency's mission.(b) Necessity includes, but is not limited to, the following circumstances:(1) When the agency determines that use of a foreign air carrier is necessary for medical reasons, including use of foreign air carrier service to reduce the number of connections and possible delays in the transportation of persons in need of medical treatment; or(2) When use of a foreign air carrier is required to avoid an unreasonable risk to your safety and is approved by your agency (e.g., terrorist threats). Written approval of the use of foreign air carrier service based on an unreasonable risk to your safety must be approved by your agency on a case by case basis. An agency determination and approval of use of a foreign air carrier based on a threat against a U.S. flag air carrier must be supported by a travel advisory notice issued by the Federal Aviation Administration and the Department of State. An agency determination and approval of use of a foreign air carrier based on a threat against Government employees or other travelers must be supported by evidence of the threat(s) that form the basis of the determination and approval; or(3) When you cannot purchase a ticket in your authorized class of service on a U.S. flag air carrier, and a seat is available in your authorized class of service on a foreign air carrier.FTR Amdt. 74, 63 FR 63419, Nov. 13, 1998, as amended by FTR Amdt. 2007-05, 72 FR 61537 , Oct. 31, 2007