So years ago we were on a US Air small commuter turbo prop, maybe twenty five seats. My husband is in a window seat, and we were ready to roll, movement started. He says, look they forgot to put the gas cap on. I thought he was kidding, I looked out on the wing and there it was laying there. I jumped up went to the cockpit, before 911 and there was just a curtain. They stopped, a ladder came out and attached it. The pilot made an announcement what had happened but stressed it wouldn’t have caused a problem. I had a good friend who was an exec pilot on a King Air and asked her, she wasn’t sure but said I think it could have gotten very quiet on that side of the plane. LOL