Image copyright Alamy Image caption The Typhoon jet (top of picture) flew at supersonic speed to reach the passenger plane

An Air India passenger plane has made a "precautionary landing" at Stansted Airport after the airline initially reported a bomb threat.

Flight AI191 was flying from the Indian city of Mumbai to Newark in the US.

The Ministry of Defence said RAF Typhoon fighter jets escorted the aircraft as it made its landing.

Air India confirmed an email came through to Mumbai airport with a bomb threat.

The airline had initially tweeted about the scare, which has since been deleted, and later told Reuters news agency the threat was a hoax.

A statement from Stansted Airport said the plane, which was carrying 327 passengers, landed at about 10:15 BST and was taken to an isolated part of the airport.

The plane finally took off for Newark at 21:30 BST.

Image caption The tweet from Air India about a "bomb threat" was deleted

Earlier, @DinoGoel tweeted to say passengers had been disembarked one by one, frisked and had their bags checked by hand and by sniffer dogs.

He said they were then put on a bus and taken to the terminal, where they were offered water and snacks.

In a later tweet, @DinoGoel said he and the rest of the passengers were being moved to Stansted main terminal.

He said: "New crew coming from London. In the mean time all passengers have to go thru [sic] security and immigration again."

An RAF spokesman said the Typhoon jets were launched from RAF Coningsby in Lincolnshire to escort the Air India plane to the airport in Essex.

He said they were authorised to fly at supersonic speed and across nearby Derbyshire, a sonic boom was heard.

The noise, which sounds like a thunder-clap, is created when an aircraft travels faster than sound - and it can cause damage to structures.

Multiple calls were made to the police and fire service from people who feared there had been an explosion.

The emergency services could not explain the cause of the loud bang heard shortly before 10:00 BST until the RAF confirmed it was their Typhoons and apologised for the inconvenience.

Ever since the Battle of Britain, RAF aircraft have been ready to respond to any incursion or incident in the air.

Today it's the job of Typhoon jets based at RAF Coningsby, covering the south of the UK, and RAF Lossiemouth to the north.

The Quick Reaction Alert (QRA) Typhoons are armed with short and medium air-to-air missiles as well as their cannon.

Crews that are on call 24/7 are expected to be in the air within minutes of being scrambled.

The RAF will first try to make radio contact with the suspect aircraft - whether it's a civilian airliner or a Russian military jet near UK airspace.

If that fails the pilots will use internationally recognised aviation signals to guide the aircraft.

Only as a very last resort would any aircraft be shot down.

That order would have to come from one of a handful of designated ministers, including the prime minister, via the RAF's command bunker at High Wycombe in Buckinghamshire.

It hasn't happened yet.