49 CFR 1546.301: Bomb or air piracy threats.

No foreign air carrier may land or take off an airplane in the United States after receiving a bomb or air piracy threat against that airplane, unless the following actions are taken:

(a) If the airplane is on the ground when a bomb threat is received and the next scheduled flight of the threatened airplane is to or from a place in the United States, the foreign air carrier ensures that the pilot in command is advised to submit the airplane immediately for a security inspection and an inspection of the airplane is conducted before the next flight.

(b) If the airplane is in flight to a place in the United States when a bomb threat is received, the foreign air carrier ensures that the pilot in command is advised immediately to take the emergency action necessary under the circumstances and a security inspection of the airplane is conducted immediately after the next landing.

(c) If information is received of a bomb or air piracy threat against an airplane engaged in an operation specified in paragraph (a) or (b) of this section, the foreign air carrier ensures that notification of the threat is given to the appropriate authorities of the State in whose territory the airplane is located or, if in flight, the appropriate authorities of the State in whose territory the airplane is to land.