41 CFR § 301-10.136 - Fly America Act exceptions for travel between the United States and another country.

(a) If a U.S. flag air carrier offers nonstop or direct service (no aircraft change) from origin to destination, the employee must use the U.S. flag air carrier service unless such use would extend travel time, including delay at origin, by 24 hours or more.

(b) If a U.S. flag air carrier does not offer nonstop or direct service (no aircraft change) between origin and destination, the employee must use a U.S. flag air carrier on every portion of the route where it provides service unless, when compared to using a foreign air carrier, such use would:

(1) Increase the number of aircraft changes made outside of the U.S. by 2 or more;

(2) Extend travel time by at least 6 hours or more; or

(3) Require a connecting time of 4 hours or more at an overseas interchange point.