The pilots were provided with the stimulant Dexedrine, generically known as dextroamphetamine and referred to as a "go-pill" by the airmen, when they set off on missions. When they returned, doctors gave them sedatives or "no-go pills" to help them sleep. Pilots who refused to take the drugs could be banned from taking part in a mission.
The use of the drugs is outlined in a 58-page document seen by The Independent entitled Performance Maintenance During Continuous Flight Operations, produced by the Naval medical research laboratory in Pensacola, Florida. It says: "Combat naps, proper nutrition and caffeine are currently approved and accepted ways ... to prevent and manage fatigue. However, in sustained and continuous operations these methods may be insufficient ..."
A statement issued yesterday by the US Air Force Surgeon General's Office confirmed the use of amphetamines by pilots. It said: "During contingency and combat operations, aviators are often required to perform their duties for extended periods without rest. While we have many planning and training techniques to extend our operations, prescribed drugs are sometimes made available to counter the effects of fatigue during these operations."
The use of stimulants by American combat pilots appears to be an open secret within the defence world, although it is believed this is the first time the Pentagon has confirmed their use was officially condoned.
The revelation has fuelled speculation that the use of amphetamines may have been a factor in a series of devastating errors by pilots that led to attacks on Afghan civilians as well as so-called friendly-fire incidents. In the worst friendly-fire incident of the campaign, four Canadian soldiers of the Princess Patricia's Canadian Light Infantry were killed and eight injured in April when an American pilot dropped a 500lb laser-guided bomb on their position.
The F-16 pilot, Illinois Air National Guard Major Harry Schmidt, had flown three hours from Kuwait to the combat zone and faced a three-hour flight back afterwards. F-16 missions from Kuwait routinely took up to nine hours.
In addition, few of the pilots based in Kuwait - where they were originally deployed to patrol the no-fly zone over southern Iraq - received the recommended 12 hours rest between missions as they were on double duty.
John Pike, director of Globalsecurity.org, a defence think-tank, said: "Better bombing through chemistry. I think [enquiring whether amphetamine use had a role in the bombing errors] is an obvious question to ask. I am surprised that the question has not been asked before.
"When you look at the original story of the [Canadian] friendly-fire incident it seems that the pilot was being inexplicably aggressive. It goes beyond fatigue or lack of experience or [being a] cowboy or trigger happy or any of the standard prosaic explanations. The simplest explanation is that the guy had eaten too much speed and was paranoid." --------------------snip