Yes I have looked at their training missions, the thing is that for the P51D there is no autopilot function, so none of their training actually commands the aircraft. However for the A-10 and modern aircraft, they use the autopilot to command the aircraft in training missions.
The best thing I have been able to do is this:
Set up the mission, AI, scene, etc ...
Fly the mission, in this case I did a startup, taxi, takeoff, and flew to a specified point.
Quit the mission, save the track.
Open track in mission editor.
Add in triggers any text or media I want to show / play at desired time stamps
Save the mission as a track
Replay the mission.
Near the end of the track, I display text that says to take control of the aircraft by pushing ESC and selecting the 'Take Control' option in the menu.
Now I have control of the aircraft, fly to my hearts delight.
This is great, because now I can simulate as if I was a student pilot, being taken on a flight to a specified training area, and then given the controls to practice stuff. The only problem is this only works up to that point. What if I wanted the aircraft to now be taken control of by the AI and RTB, taxi, park, and shutdown? I don't know of any way to play a track, or allow a track to take control during gameplay, seems impossible. The only thing that I am seeing that might be able modify controls in game run time is maybe LUA script, which I am not familiar with at all.