Answer:
I'm sure after a take off to get to their destination, and after the arrival they have been flying in a plane, their body might sometimes not know how to react if it's their first time. Sometimes people need to vomit but I dont think they would have time to unbuckle their Seat belts and rush to the bathroom, instead people who work with the airplanes thought about it first, they have barf bags so they can vomit on. Some peoples bodies react differently.