An RAF fighter jet tasked with defending the Olympics against terror attacks was scrambled after an aircraft lost contact with aviation authorities, the Ministry of Defence has said.
The Typhoon was sent to intercept the aircraft after air traffic controllers lost contact.
But the jet was able to return to its base at RAF Northolt, west London, shortly after taking off when communication was re-established with the pilot.
An MoD spokesman said it was at least the third time Typhoons have been scrambled since the start of the Olympics on July 27 but was unable to confirm the type of aircraft involved in this latest incident although he said it was flying outside London's restricted flying zone.
Four Typhoon jets are on standby to intercept aircraft suspected of posing a terror threat throughout London 2012.
The fighters, which can travel at up to 1,370 miles per hour, are normally based at RAF Coningsby in Lincolnshire and RAF Leuchars in Fife to defend UK airspace but have been stationed at RAF Northolt during London 2012.
It is the first time they have been based at the airfield since the Second World War.
Twitter users were quick to spot the Typhoons flying through London's skies.
Hayley Taylor tweeted: "A Eurofighter Typhoon just flew over my house. It means trouble when those bad boys take off!" while another user named JimBaww wrote: "Eurofighter jets circling in London.#PrettyCool."
Matthew Sheppard tweeted: "Eurofighter just flew overhead at very high speed heading towards Central London. Loud."