19 CFR 122.61 - Aircraft required to clear.
(a) Private aircraft leaving the United States as defined in § 122.22, for a foreign area are required to clear as set forth in § 122.26. All other aircraft, except for public aircraft leaving the United States for a foreign area, are required to clear if:
(1) Carrying passengers and/or merchandise for hire; or
(2) Taking aboard or discharging passengers and/or merchandise for hire in a foreign area.
(b) Any aircraft used by members of air travel clubs are required to clear, and foreign aircraft traveling under a permit to proceed shall also clear.