41 CFR 301-10.135: -10.135 Fly America exceptions for foreign air carrier service as a necessity.

(a) Foreign air carrier service is deemed necessary when U.S. flag air carrier service is available but—

(1) Cannot provide required air transportation; or

(2) Will not accomplish the agency's mission.

(b) Necessity includes circumstances such as:

(1) Medical reasons, including reducing connections and potential delays for individuals needing medical treatment.

(2) Avoiding unreasonable risks to employee safety, which requires a case-by-case agency determination and written agency approval.

(3) Threats against U.S. flag air carriers, which must be supported by a travel advisory notice from the Federal Aviation Administration and Department of State.

(4) Threats against a Government employee or other travelers, which must have evidence supporting the threat that form the basis of the agency's determination and approval.

(5) Inability to purchase a ticket in the authorized service class on a U.S. flag air carrier, and there is an available seat in the authorized service class on a foreign air carrier.