The background as it stands is totally black and matting out the cockpit where no information exists & then tracking its motion for the matte is bloody difficult.
suggestion for this.
if I'm right, I think the other cockpit shots which DO feature the trench rushing by are from the same camera angle.
so, instead of making it hard to mask, you can use the other shots to establish a seperate mask for the cockpit frames you can't see at the back of the cockpit. then you can use the foreground cockpit frames that are visible to keep the whole mask lined up right. might make it a bit easier.