High - altitude military parachuting 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 . In typical HALO / HAHO insertions , the troops are dispatched from altitudes between and . HALO - High Altitude Low Opening . The origins of the HALO technique 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 . Stapp , a research biophysicist and medical doctor , used himself as a human guinea pig in rocket sled tests to study the effects of very high g - forces . Stapp also resolved many of the issues involved in high altitude flight in his earliest work for the Air Force , and subjected himself to exposure to altitudes of . Subsequently , he helped develop pressure suits and ejection seats , which have been used in jets ever since . As part of the experiments , on August 16 , 1960 , Colonel Joseph Kittinger performed the first high altitude jump at an altitude of above the Earth ' s surface . The first time the technique was used for combat was during the Vietnam War in Laos by members of MACV - SOG . SEAL Team Six of the United States Navy expanded the HALO technique to include delivery of boats and other large items in conjunction with parachutists . The technique is used to airdrop supplies , equipment , or personnel at high altitudes when aircraft can fly above surface - to - air missile ( SAM ) engagement levels through enemy skies without posing a threat to the transport or load . In the event that antiaircraft cannons are active near the drop zone , the HALO technique also minimizes the parachutist ' s exposure to flak . For military cargo airdrops , the rigged load is cut free and rolls out of the plane as a result of aircraft deck angle ( ADA ) . The load then proceeds to fall under canopy to a designated drop zone . In a typical HALO exercise , the parachutist will jump from the aircraft , free - fall for a period of time at terminal velocity , and open his parachute at a low altitude . The combination of high downward speed , minimal metal and forward air - speed serves to defeat radar as well as simply reduce the amount of time a parachute might be visible to ground observers , enabling a stealthy insertion . HAHO - High Altitude High Opening . The HAHO technique is used to airdrop personnel at high altitudes when aircraft are unable to fly above enemy skies without posing a threat to the jumpers . In addition , HAHO parachute jumps are employed in the covert insertion of military personnel ( generally special operations forces ) into enemy territory , in circumstances where the covert nature of an operation may be compromised by the loud noise of parachutes opening at low altitude . HAHO jumps also allow a longer travel distance due to increased under canopy time , allowing travelling distances of more than 40 miles ( 64 km ) . In a typical HAHO exercise , the jumper will jump from the aircraft and deploy the parachute at a high altitude , 10 – 15 seconds after the jump ( typically at or so ) . The jumper will use a compass or GPS device for guidance while flying for 30 or more miles . The jumper must use way points and terrain features to navigate to his desired landing zone , and correct his course to account for changes in wind speed and direction . If deploying as a team , the team will form up in a stack while airborne with their parachutes . Usually , the jumper in the lowest position will set the travel course and act as a guide for the other team members . Whilst in the British Special Forces ( 22 SAS ) , due to his extensive skydiving background , Charles " Nish " Bruce was pivotal in the original trials & development of the HAHO tactic now routinely used as a conflict insert for Special Forces . Health risks . All types of parachuting technique are dangerous , but HALO / HAHO carry special risks . At high altitudes ( greater than 22 , 000 feet [ 6 , 700 m ] ) , the partial pressure of oxygen in the Earth ' s atmosphere is low . Oxygen is required for human respiration and lack of pressure can lead to hypoxia . Also , rapid ascent in the jump aircraft without all nitrogen flushed from the bloodstream can lead to decompression sickness ( also known as caisson disease or " the bends " ) . A typical HALO exercise will require a pre - breathing period ( 30 – 45 minutes ) prior to jump where the jumper breathes 100 % oxygen in order to flush nitrogen from their bloodstream . Also , a HALO jumper will employ an oxygen bottle during the jump . Danger can come from medical conditions affecting the jumper . For example , cigarette smoking , alcohol and drug use ( including histamine antagonist s , sedatives , and analgesic s ) , anemia , carbon monoxide , fatigue and anxiety can all lead to a jumper being more susceptible to hypoxia . In addition , problems with the oxygen bottle and during the changeover from the pre - breather to the oxygen bottle can result in the return of nitrogen to the jumper ' s bloodstream and , therefore , an increased likelihood of decompression sickness . Theoretically , a single breath of atmospheric air may elevate the jumper ' s arterial nitrogen level to dangerous levels . A jumper suffering from hypoxia may lose consciousness and therefore be unable to open his parachute . A jumper suffering from decompression sickness may die or become permanently disabled from nitrogen bubbles in the bloodstream , which causes inflammation of joints . Another risk is from the low ambient temperatures prevalent at higher altitudes . At an altitude of 35 , 000 feet , the jumper faces temperatures of – 45 °C ( – 50 °F ) , and can experience frostbite . However , HALO jumpers generally wear polypropylene knit undergarments and other warm clothing to prevent this . HALO carries the additional risk that if the parachute fails to deploy or lines become tangled , there is less time to resort to the reserve ( back - up parachute ) or untangle the lines , though the reserve is the best option if this were to occur . Typical equipment . In a typical HALO exercise , a parachutist will jump with : The 2012 Relativity Media film , " Act of Valor " features an MFF insertion of SEAL Team 7 into hostile territory .