The key word there is "guaranteed". I'd much rather know that I'm going to spend 1-2 hours at the airport, than have no idea. On a leave-when-full plane, you

The key word there is "guaranteed". I'd much rather know that I'm going to spend 1-2 hours at the airport, than have no idea. On a leave-when-full plane, you may be there for any length of time from 20 minutes (if you are one of the last to arrive), to maybe 2 hours (if you are one of the first to arrive), to maybe 4 hours (if you arrive just as the last one leaves, and there isn't another one arriving for a while).