When I first ran FSX I was missing the option to play ATC in single player mode.
Yesterday I was in the tower during a multiplayer game and the host ended the session. The popup box appeared asking me if I wanted to continue "flying". I selected yes.
and there I was in the tower, computer generated traffic appeared on the ground and in the air. I could do everything that the tower controller can do during multiplayer.
Downside, computer generated traffic is even worse than real life players when in comes to listening to ATC commands, there where no radio menu options like you get as a pilot in single player mode either.
Would be a nice addon to get this to work in single player mode though.

