In the scene where Holly Hunter jumps up on Richard's bomber to kiss him and tell him she loves him (his last takeoff before he gets himself blown up), I noticed something unusual.

Dreyfuss has some kind of white rag sitting on top of the canopy of his plane. As he stands up to greet Holly it seems like he notices it and brushes it out of the way very quickly (as if he didn't want it to be in the shot, like it shouldn't be there).

I can't think of any good reason for that rag to be sitting up there in real life, But I did notice what looked like raindrops on the bomber's canopy.

Perhaps it rained briefly before they filmed that scene and the rag was there to dry things off before they resumed the shot?