Jets were scrambled to intercept a cargo plane south of London today as part of the RAF's Quick Reaction Alert system, which has been tasked with defending British airspace since 1940.
Two air bases share this duty: RAF Coningsby in Lincolnshire generally covers the south, and RAF Leuchars in Fife looks after the north.
The procedure that would lead to Typhoon jets being scrambled is described here by Flight Lieutenant Noel Rees:
At the start of the scaled QRA response, civilian air traffic controllers might see on their screens an aircraft behaving erratically, not responding to their radio calls, or note that it’s transmitting a distress signal through its transponder.
Rather than scramble Typhoons at the first hint of something abnormal, a controller has the option to put them on a higher level of alert, ‘a call to cockpit’. In this scenario the pilot races to the hardened aircraft shelter and does everything short of starting his engines. From this posture a controller can monitor a situation knowing that a scramble can be conducted in moments.
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