Casualty evacuation, also known as CASEVAC or by the callsign Dustoff or colloquially Dust Off, is a military term for the emergency patient evacuation of casualties from a combat zone. Casevac can be done by both ground and air. "DUSTOFF" is the callsign specific to U.S. Army Air Ambulance units. CASEVACs by air today are almost exclusively done by helicopter, a practice begun on a small scale toward the end of World War II; before that, STOL aircraft, such as the Fieseler Fi 156 or Piper J-3 were used.