By Jonathan Beale 
 
 Defence correspondent, BBC News 
 
 Fighter jets were scrambled to intercept a United Airlines flight RAF Typhoon fighter jets have been scrambled twice this month amid fears of possible terror threats in UK airspace, the BBC has learned. Eurofighter Typhoons took off from the quick reaction alert base at Coningsby in Lincolnshire – one of two such bases in the UK – minutes after warnings of suspected attempts to hijack American airliners. Ultimately the minister would make the difficult decision to intervene or, if all else fails, to shoot an aircraft down. Last Monday British air traffic control picked up the words "hostage" and "ransom" from a United Airlines plane bound for Frankfurt in Germany. Soon afterward a Delta Airlines plane - on its way from the US to Frankfurt - made what is described as an "unusual request" to descend just as it was flying south of Reading. Pilots of the Typhoons at Coningsby and RAF Tornado F3 fighters at Leuchars in Fife – the UK's other quick reaction alert base – were immediately briefed and ordered to intercept the airliner. It was, thankfully, a false alarm. From there, 10 Downing Street is alerted, where officials are ready to warn the prime minister that he may have order an RAF pilot to shoot down a civilian airliner. There is a terrorism alert involving civil airliners in British airspace about once a month – out of some three million which cross it every year – officials say.
– Britain's Royal Air Force has scrambled fighter jets twice this month after receiving warnings of possible attempts to hijack American passenger jets, defense sources say. Both incidents proved to be false alarms but they have put fresh focus on Britain's post 9/11 counterterrorism procedures for commercial aircraft, the BBC reports. The Guardian notes that PM Gordon Brown was alerted, and could have faced the decision of whether to shoot an airliner down to avoid a potential attack. In the most recent incident, fighter jets were scrambled after air traffic controllers overheard the words "hostage" and "ransom" in a conversation on a flight from the US, followed by a highly unusual request to carry out a sudden descent to test auxiliary power units. The jets followed the aircraft through UK airspace and into Belgium, where it landed. Defense officials said the matter was resolved but declined to provide further details.