Since you guys are talking about multiplayer mode, I just wanna add what we're working on.
We're implementing "Freeway" multiplayer mode. Main point will be you can join race at any time and drop out if you wish. If there are not enough players coming in all the time, server will start adding random recent replays, so race is always full. Basically planes will be all over the track. Your time will be compared to planes that finished recently before you.
I guess it will be a blend between real-time multiplayer and license mode. Hopefully it will be fun.