RAF Typhoon jets have caused a sonic boom after they scrambled to intercept a plane near Stansted Airport, it is alleged tonight.
It caused an almighty bang which has been heard as far as 18 miles away in Chelmsford, Essex.
Unconfirmed reports say no planes are leaving or taking off at the hub.
But the airport told Mirror Online operations are running as normal.
Sources on Twitter claimed the RAF sent two typhoon jets from their base in Coningsby, Lincolnshire, to escort a plane to Stansted after a passenger became disruptive.
An RAF Voyager also departed from RAF Brize Norton, Oxfordshire, it is said.
Emergency services have been urged to longer ring 999.
The Bishop Stortford Police Twitter account said: "Large number of 999 calls coming in about a loud explosion. We have liaised with @EssexPoliceUK who are confirming that this is a sonic boom from a passing aircraft."
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A sonic boom is a loud explosive noise caused by the shockwave of an aircraft travelling faster than the speed of sound.
A statement from Hertfordshire Fire Control reads: "We've been made aware by the Police that this was a sonic boom from the Stansted airport area. Police received numerous calls and we received calls from the Bishop's Stortford area."
But people on Twitter are reporting they've experienced an "explosion" and heard a massive "bang". Those tweeting live as far as parts of east London.
One panicked resident said online: "Just heard a massive explosion."
Another posted: "Was there just a massive explosion in Harlow?"
A third saw "windows on [their] house shake..."
Others at the airport said their flights were delayed.
"Runway has reopened and planes are landing now," one man wrote.
"Not sure how long the whole thing lasted. Our flight to Denmark is delayed (as I'm sure others are from the disruption). There was a sonic boom in relation to the incident earlier but I didn't realise it was that at the time."
A graphic shared by one aviation expert shows the flight path of a typhoon, believed to have left RAF Coningsby in Lincolnshire and headed south tonight.
Essex Police has been contacted for comment.
