One of five men arrested near RAF Fairford in the early hours of Sunday morning had dialled 999 himself, the BBC understands.
The suspect called the police at 00:45 BST, almost an hour before a female farmer also dialled 999 after seeing men in balaclavas.
The five were arrested on suspicion of explosives offences and later terrorism offences after three vans were spotted, sparking a major security incident around the Gloucestershire base which the US military operates.
