blood chit

plural blood chits

1. A notice carried by military personnel, addressed to any civilians who may come across them when they are in trouble, requesting that assistance be offered to them in such situations.
2. A form signed by a passenger on a private or military aircraft, granting indemnity to the flight operator against any accident.

   When I had signed the 'blood chit', giving Air Ministry indemnity in case of accidents, we were ready to take off.

   2009, Antony Chessell, A Small Share in the Conflict, page 49

   1 more example

   I was then made to sign a "Blood Chit" known as an "Indemnity Bond". Dick then took me to an aircraft, jumped into the cockpit and strapped me to the seat together with a parachute.

   1958, P. N. Sharma, Inside Pak Occupied Kashmir, page 19