Without you moving? Not seen that before

it sometimes happens if you change the mission player aircraft for a more powerful one, & i think it's the computer compensating by reducing the wingmen, sounds nuts i know, it happens too often for it to be a coincidence. The only other thing is a bug in the mission itself, wrong height setting for the wingmen, engines not on etc. Have a go at changing things in 'Mission Builder' if you keep the original download outside CFS2 & just copy & paste into missions folder you can just replace the altered files as you want if it's NBG, thats how i got into it, trial & error.
Happ
