Two soldiers were caught having sex in an Apache helicopter that was "swaying side to side".
The pair, believed to be drunk, were in the back of a two-seater helicopter and found half-naked by their fellow squaddies.
The ground crew was going to the Apache to put rain covers on it after a night-time servicing when they heard unusual noises while the rotors swayed.
An air safety report revealed: "It became apparent that the rear cockpit was occupied by two people engaged in sexual intercourse.
"Both parties were serving soldiers. Both showed symptoms of intoxication."
The pair were naked from the waist down - a man in uniform and a woman in civilian clothing.
They were ordered to get dressed and get out of the helicopter.
The Apache belonged to the Army Air Corps' 653 Squadron but the soldiers were from a separate unit, thought to be Royal Artillery.
The Military Aviation Authority report added: "They were detained until the chain of command of 653 Squadron and their parent unit arrived."
An Army source told the that the incident happened at the Otterburn range in Northumberland in 2016, but has just become public due to a computer glitch.
The air crew were ordered to secure choppers in future, the source added.
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