Its in the booklet, page 11 - 'Tactical Control' single missions only where stated in the briefing. If your plane suffers damage and the handling is compromised you can switch to another one in your flight group, your plane will still be piloted but your wingman will have the duff plane. Or, assign a pilot to a target, if he can't do the buisiness you can take over....
Using tactical control allows you to prevent being killed as there are limited attempts to complete the mission.
Plenty of SIM games last night (which I really enjoyed) even though my Kill rate plummets, managed two in about 6 games. Much more satisfying when you do get a kill and the guys in my team were very patient and didn't mind having a pretty useless rookie like me. Best game was organised into Axis v Allies which made spotting the enemy far easier and lots of chat concerning who was where and on whose tail makes for a really fantastic experience.