I guess that would be enough if it's possible to do it for all the big aircrafts, like commercial jets.
Actually I was thinking about RPG and this idea. You could have an airline on some RPG server, sell tickets to others and then transport them to other airport.
But what about boats? There are empty seats visible, but you cannot get on them as passenger....
Btw, all of these experiences are based on SA-MP, so I dunno if MTA:SA will differ alot in these things...