Anti-terror jets vigil revealed Last updated at 02:30am on 28th December 2006 Tornado jet fighters are scrambled regularly from UK bases to intercept any aircraft behaving oddly in British airspace, the head of the RAF has disclosed. Air Chief Marshal Sir Glenn Torpy, the Chief of the Air Staff, said there had been at least one incident per month since the 9/11 attacks requiring an RAF fighter from a quick alert unit to intervene. He told The Times newspaper: "The Tornados have been launching pretty regularly for any aircraft that appear to be behaving oddly: for instance, where airline pilots fail to communicate with flight control or take an unexpected route." And he added: "We are pretty acutely aware of the short time that we have to respond to these incidents. If there is any doubt at all about an aircraft, we launch the Tornados." The counter-terror operation - which includes interception of commercial airliners - is costing taxpayers tens of thousands of pounds. The bill for keeping a Tornado airborne for an hour is up to Â£9,000. Four quick-reaction Tornado F3 planes are on permanent standby to intercept any plane that deviates from strict flight control procedures, The Times reported. Two are at RAF Marham in Norfolk and two at RAF Leuchars, in Fife, eastern Scotland. The RAF chief told the paper of an incident last month when the captain of a North West Airlines plane flying from Paris to Detroit asked to divert into UK airspace because of a disruptive passenger. The flight was shadowed by an already airborne Tornado F3 before the airline pilot was put on route to Prestwick. Fighter pilots were last regularly scrambled to monitor planes in UK airspace during the Cold War.