Exactly! There isn't an airline in the world (or at least in North America) that doesn't require you to pay in advance!
I nearly got bumped from a flight overseas that I'd booked months in advance. If I hadn't gotten on, I'd have missed a connection on the other end that only happens twice a week. I kicked up a bit stink about it and got on, but it was my first experience with overbooking and bumping and I was not impressed.