Two Typhoon jets scrambled to an aircraft that had lost communications caused a sonic boom in the early hours of Sunday.
Residents across Hertfordshire and north London were woken by a loud bang, feared by some to be from an explosion.
The RAF said the fighter planes were deployed from RAF Coningsby in Lincolnshire shortly before 4.10am.
The aircraft were the cause of an explosion-like sound which was heard across vast swathes of the South East, with Hertfordshire Fire and Rescue receiving a "large number" of calls.
An RAF spokeswoman said: "Two Typhoon fighter aircraft from RAF Coningsby were scrambled at 0409 this morning, as part of the UK's Quick Reaction Alert procedures, after an aircraft lost communications in UK airspace.
"The aircraft was intercepted and its communications were subsequently re-established. The Typhoons are returning to their base."
Shortly after 4am, the Metropolitan Police received reports of the “loud bang” and tweeted there are no reports of an explosion.
Officers began looking into the cause behind the noise and soon confirmed RAF jets were behind the sound.
The Met initially tweeted: “We are aware of reports of a loud bang in the north London area. There are no reports of an explosion and police are looking into the incident.
“There is no cause for public concern.”
Just minutes later, police confirmed: “The loud bang heard throughout north London and surrounding areas was the result of a sonic boom from RAF planes. There is no cause for concern.”