Whilst all members of the SAS are required to be fully parachute and line jumping trained, free-fall troop take these skills further by utilising High Altitude High Opening (HAHO) jumps and High Altitude Low Opening (HALO) jumps.
The main advantage of parachuting into an operation is the covertness of such insertions, in addition HAHO jumps mean the patrol can be inserted from friendly airspace but drop well behind enemy lines for covert reconnaissance, patrols or offensive missions.
‘High Altitude, High Opening is employed by the SAS for insertion into hostile terrain. The trooper, wearing an oxygen mask, exits the aircraft at 10,000 metres, free falls for 8-10 seconds, then deploys his ‘chute at around 8500 metres. He then makes a gentle flight to the ground – which can take between 70 and 80 minutes – by which time he will have travelled a distance of up to 30 kilometres. [He will use his GPS equipment to navigate to his landing zone (LZ) where hopefully he’ll meet up with the rest of his patrol.]
The advantage of HAHO parachuting is that SAS teams can leave an aircraft outside hostile areas and land silently inside enemy territory, without the noise of their aircraft alerting the opposition. – HAHO was used in the 1991 Gulf War.
High Altitude, Low Opening is similar to HAHO in that the trooper exists the aircraft at 10,000 metres, except the chute is deployed at around 760 metres. HALO allows SAS teams to land together, an important factor considering most operational HALO descents are conducted at night.’ HALO can also be used for insertion into water.
(‘A-Z of the SAS’, Peter Darman. 1992. Sidgwick & Jackson )