If I'm at the field when that happens I use some 3M Clear Package Tape. Works quite well. For a more permanent fix I use some scrap covering of whatever happens to be on the plane. I cut a round piece or at least with rounded corners (to prevent dog-ears) with an overlap of about 1/4 - 3/8 of an inch all the way around. Seal it down with the iron, let it cool, then use the tip of the iron to shrink it in the center. Try not to touch the part that is already adhered or it might soften the adhesive and allow it to slip.