19 CFR § 122.88 - Aircraft carrying domestic (stopover) passengers.
Airlines that commingle domestic (stopover) passengers (that is, passengers who have already cleared Customs at their port of arrival and are continuing on another aircraft to a second U.S. destination) with international passengers who are continuing on the flight to their port of arrival and have not yet cleared Customs, must comply with certain requirements before being issued a permit to proceed. The carriers requirements are as follows:
(b) A $2.00 charge must be paid for each revenue producing domestic (stopover) passenger reinspected in the U.S. (see § 24.12 of this chapter).
(c) Arrangements must be made for the checked baggage of all passengers requiring inspection on the previously described flights to be off-loaded and made available for examination in the Federal inspection area at the destination port (intermediate or final) where an inspection is to take place.
(d) All stopover passengers shall be notified in writing, prior to boarding, that they will be subject to full reinspection by Customs. This written notification shall contain the following language: “Notice to all boarding passengers: You are boarding an aircraft on which passengers will be arriving in the U.S. from foreign destinations. These passengers have not yet cleared U.S. Customs. Accordingly, you will be subject to a full reinspection by Customs at your final U.S. port of entry.”
(e) Domestic (stopover) passengers shall be provided a Customs declaration identified by the words “Domestic Flight”. The domestic (stopover) passenger is only required to complete items 1-4 on that declaration.
(f) The carrier shall present to Customs, as otherwise required by law, the permit to proceed and/or the general declaration, clearly stating the number of domestic (stopover) passengers to be reinspected upon arrival at the destination port (intermediate or final) where an inspection of passengers is to take place.