19 CFR §122.35

1. (a)Application. This section applies to emergency or forced landings made by aircraft when necessary for safety or the preservation of life or health, when such aircraft are:
   1. (1)Travelling from airport to airport in the U.S. under a permit to proceed (see §§ 122.52, 122.54 and 122.83(d)), or a Customs Form 7509 (see § 122.113); or
   2. (2)Coming into the U.S. from a foreign area.
2. (b)Notice. When an emergency or forced landing is made, notice shall be given:
   1. (1)To the Customs Service at the intended place of first landing, nearest international airport, or nearest port of entry, as soon as possible;
   2. (2)By the aircraft commander, other person in charge, or aircraft owner, who shall make a full report of the flight and the emergency or forced landing.
3. (c)Passengers and crewmembers. The aircraft commander or other person in charge shall keep all passengers and crewmembers in a separate place at the landing area until Customs officers arrive. Passengers and crewmembers may be removed if necessary for safety, or for the purpose of contacting Customs.
4. (d)Merchandise and baggage. The aircraft commander or other person in charge shall keep all merchandise and baggage together and unopened at the landing area until Customs officers arrive. The merchandise and baggage may be removed for safety or to protect property.
5. (e)Mail. Mail may be removed from the aircraft, but shall be delivered at once to an officer or employee of the Postal Service.