Old May 21, 19, 4:16 pm
Join Date: Feb 2001
Location: SEA once more (previously CDG and NRT)
Programs: DL DM, UA Silver, Marriott Gold
Posts: 2,201
Either one of them could check. “Responsibility” to check isn’t really the right way to think of it, as neither are required to.

Airlines check because if they deliver a passenger without proper docs, they get fined and have to also bear the cost of flying the passenger back. So the reason they check is because if their own self interest - they want to avoid those fines and costs.

The carrier flying the domestic segment doesn’t have any exposure to those risks, so there is a good chance they won’t perform the checks.
SEA-Flyer is offline