Britain's Ministry of Defence scrambled a Typhoon fighter jet on Wednesday after an aeroplane lost contact with air traffic controllers.
The move comes amid heightened security in London, just two days ahead of the Olympics opening ceremony.
The Ministry of Defence said the commercial aircraft did not enter restricted airspace over London, but had lost contact with air traffic control, prompting the launch of a Typhoon shortly after noon.
Communications were quickly restored and no further action was required, the ministry added.
Typhoons are part of the Ministry of Defence's multi-tiered security plan for the upcoming games, which will also rely on thousands of troops, warships, surveillance aircraft and sniper-toting helicopters.