Hm... I'm not a 100% sure but I still belive it's the wind. According to the Rubicon it's 17 m/s, which is close to a gale ;) pretty sure one shouldn't go fly helicopters in that. I can try to remove the wind in the mission editor, see if it makes a difference.
EDIT:
Indeed, I removed the wind in mission 4 (The one where you must destroy a EW radar), and I got clearence to startup straightaway, and my wingman did the same. The mission used the dynamic weather system by default, so that's probably why I got clearence after waiting a bit when I played the mission the first time.