None of the relevant contracts allow for you to specify the plane. If you buy a ticket for "an airbus A350" and show up and they ask you to board a 737, if you

None of the relevant contracts allow for you to specify the plane. If you buy a ticket for "an airbus A350" and show up and they ask you to board a 737, if you refuse, you are the one breaking the contract, and the airline does not have to compensate you in any way. Right now a significant majority of all flights happen on the exact model of aircraft the ticket mentioned, but if people start choosing not to fly on boeings, you can rest assured that airlines will start to move planes around so that their expensive planes still make money. If you want to be guaranteed the plane you signed up for, we need new regulation. That is not a right anyone has currently.