A dead head is an airline crew member, a pilot or a cabin crew, who is assigned to fly to a particular destination to assume a duty. In the flight where he or she is in, she’s not supposed to work as a crew. He or she shall be in a complete uniform, thus making him or her able to sit on a jumpseat if the flight is full. Deadheading crew are also paid based on their flying time.

A dead head crew is different from a non-revenue. Crew member who use non-rev tickets are using their company’s benefits for their personal travels. If a flight is full and there are no available jumpseats, a deadheading crew can bump off a revenue passenger. However if the flight is full, a revenue passenger or a non-rev crew cannot bump off a deadhead. Non-revs are not allowed to sit on the jumpseat, not unless they are in their full uniform, and as per the captain.

As to most airlines, sitting on a jumpseat makes you an “able crew”. Meaning in case of an emergency, you will be able to assist the operating crew and passengers during evacuation.