Kenneth Ecott, 26, went to sleep with a group of people, including the alleged victim, after a house party in Poole.
The 15-year-old told the court she woke to find Mr Ecott naked on top of her and started screaming in the early hours of 19 November last year.
Mr Ecott denied one count of rape and the jury at Bournemouth Crown Court took two hours to clear him.
"I was stood outside completely naked in the middle of the street wondering what the hell I was doing there"
The Senior Aircraftman had been celebrating a birthday with friends at the Royal British Legion club in Poole, before they went back to a friend's house to continue the party.
The trial heard he shared a bottle of vodka with others at the house before a number of them fell asleep on inflatable mattresses in the dining room.
Mr Ecott told police during an interview he could not remember anything between falling asleep and finding himself naked on the street.
The court heard other people at the party told him "he had sex with the teenager", who cannot be named for legal reasons.
He told the court: "It was like being shot in the chest. I couldn't believe what I had just heard."
Mr Ecott was arrested at his barracks in RAF Brize Norton, Oxfordshire, later on the day of the alleged incident.
He did not deny having sex with the girl but told detectives in Poole he had been sleepwalking and was "not aware of his actions as he had been in a state of automatism".
'Night terrors'
The court heard he said during an interview: "I laid down to go to sleep.
"The next thing I knew I was stood outside completely naked in the middle of the street wondering what the hell I was doing there."
Mr Ecott's father was killed in an incident when he was 12 and his mother died of cancer five years later, the court heard.
The jury also heard he suffered "night terrors" and had once punched his girlfriend during a bad dream, but had no recollection of it afterwards.
Mr Ecott joined the RAF in June 2004 and worked as a telecommunications operator maintainer, responsible for running IT services in air force and army bases.
He served for four months in Iraq and then went to Afghanistan for three months to run the IT services at a base in Kandahar.
The court heard he was not sleeping properly because of jet lag on returning from Afghanistan on 16 November, days before the party.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~58~RS~)