49 CFR § 1544.303 - Bomb or air piracy threats.
(a) Flight: Notification. Upon receipt of a specific and credible threat to the security of a flight, the aircraft operator must—
(1) Immediately notify the ground and in-flight security coordinators of the threat, any evaluation thereof, and any measures to be applied; and
(2) Ensure that the in-flight security coordinator notifies all crewmembers of the threat, any evaluation thereof, and any measures to be applied; and
(3) Immediately notify the appropriate airport operator.
(b) Flight: Inspection. Upon receipt of a specific and credible threat to the security of a flight, each aircraft operator must attempt to determine whether or not any explosive or incendiary is present by doing the following:
(1) Conduct a security inspection on the ground before the next flight or, if the aircraft is in flight, immediately after its next landing.
(2) If the aircraft is on the ground, immediately deplane all passengers and submit that aircraft to a security search.
(3) If the aircraft is in flight, immediately advise the pilot in command of all pertinent information available so that necessary emergency action can be taken.
(c) Ground facility. Upon receipt of a specific and credible threat to a specific ground facility at the airport, the aircraft operator must:
(1) Immediately notify the appropriate airport operator.
(2) Inform all other aircraft operators and foreign air carriers at the threatened facility.
(3) Conduct a security inspection.
(d) Notification. Upon receipt of any bomb threat against the security of a flight or facility, or upon receiving information that an act or suspected act of air piracy has been committed, the aircraft operator also must notify TSA. If the aircraft is in airspace under other than U.S. jurisdiction, the aircraft operator must also notify the appropriate authorities of the State in whose territory the aircraft is located and, if the aircraft is in flight, the appropriate authorities of the State in whose territory the aircraft is to land. Notification of the appropriate air traffic controlling authority is sufficient action to meet this requirement.