Sci-fi series aside, these black and red, triangle-shaped stickers are actually important reference points for the flight crew — as they're located where the airplane's wings are visible — allowing flight attendants to easily view the flaps and slats on the wings for potential icing problems or issues that may need to ...
If there is a problem on-board and the crew is unsure about the condition of the aircraft, the triangle indicates what window should be used to inspect flaps, slats or engines or look out for icing. This saves important time in case of an emergency, as the crew doesn't has to search the right window to look out.
A deadhead flight is another name for an empty legs flight. This is a flight that occurs when an aircraft has been used for a one-way jet charter and has to either return to its base or fly to another airport to pick up its next passengers.
Airplanes' wings are curved on top and flatter on the bottom. That shape makes air flow over the top faster than under the bottom. As a result, less air pressure is on top of the wing. This lower pressure makes the wing, and the airplane it's attached to, move up.