Upvote:1
Can I buy a US domestic ticket for Europeans visiting the US?
YES. 100%.
Is there a problem buying them a ticket on a US airline to do so?
NO, not at all.
Just make sure the name on the reservation matches their Passport and they're good to go.
Upvote:3
There is no problem, so long as your relatives can present identification documents that match the names on the tickets.
You are not asked for your nationality when booking a domestic flight, and there is no special identification required of aliens at the TSA checkpoint. Furthermore, I don't see how it would ever make senseβ economically, politically, or otherwiseβ for an airline to restrict a particular flight to passengers of a certain nationality.