Blood Chits, also called Identification or Rescue Flags, were designed to provide rapid identification of a downed flyer and facilitate assistance from local allies encountered.
The flag of the issuing government is usually at the top, followed by a message in one or more local languages. The first ever use of Blood Chits by American flyers was in the China Burma India Theater of World War II. They were used by the 14th Volunteer Bomb Group and by the Flying Tigers of the American Volunteer Group (AVG) operating in China. The first recorded use of what came to be known as a Blood Chit was by members of a British Royal Flying Corps squadron in India in 1917. It is believed that contact between the AVG and the RAF in Burma in 1941 may have led General Chennault to create a version of the Blood Chit for use by the AVG.