An armed US air marshal was taken off a plane at Heathrow airport and arrested after being accused of being drunk.
The United Airlines flight to Los Angeles was two hours late taking off after the captain alerted police that the man was under the influence of alcohol.
The federal marshal - believed to have been one of four who were on board the Boeing 777-200 - was breathalysed at the London airport's police station, but later released without charge.
After the 9/11 terror attacks, the job of US air marshals is to "detect, deter and defeat hostile acts". They operate a "shoot to stop" policy and also carry a baton and handcuffs.
Under US rules, they are banned from drinking at least four hours before a flight and must not have any trace of alcohol in their blood when on duty and armed.
However, the man taken off Flight 935 at Heathrow was released without charge because he is not believed to have broken any UK laws.
A police source told The Sun: "It is only an offence if someone has an aviation function like flying the plane or being an engineer.
"When the case was reviewed it was decided the legislation did not fit with the function he performed."

A Metropolitan Police spokesman said: "On Monday, May 9, police were called at around 12.25pm following concerns by the captain of a flight due to leave Heathrow for Los Angeles that a person trying to board was under the influence of alcohol.
"Officers attended and breathalysed a man, and he was subsequently arrested on suspicion of being over the prescribed limit.
"The man was taken into custody at Heathrow Police Station, but released shortly after with no further action."
A United Airlines spokesman said: "We apologise to our customers for any inconvenience caused by the delay."
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