High-altitude military parachuting (or military free fall (MFF)) is a method of delivering personnel, equipment, and supplies from a transport aircraft at a high altitude via free-fall parachute insertion. Two techniques are used: HALO (high altitude - low opening) and HAHO (high altitude - high opening).
In the HALO technique, the parachutist opens his parachute at a low altitude after free-falling for a period of time, while in the HAHO technique, the parachutist opens his parachute at a high altitude just a few seconds after jumping from the aircraft. HALO techniques date back to 1960 when the U.S. Air Force was conducting experiments that followed earlier work by Colonel John Stapp in the late 1940s through early 1950s on survivability factors for high-flying pilots needing to eject at high altitudes. In recent years, the HALO technique has been practiced by civilians as a form of skydiving. HALO is used for delivering equipment, supplies, or personnel, while HAHO is generally used only for personnel.