"우리는 비행기표를 예매했습니다."
Translation:We booked plane tickets.
Yes, "plane tickets" is the most common where I live. "Airplane tickets" is a trailing second. I think the phrase I've seen others use here, "airline tickets" is strange but acceptable. I don't really visit airline companies but maybe it's a new hipster thing. "Flight tickets" could work too, better than "airline tickets" to me. And then you can head-drop ticket from any of these and say you "booked a(n) X" (-tickets).