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An MoD spokesman said the incident was now a police matter and "our involvement is over".
He said Typhoon jets can be scrambled after the pilot or crew of a passenger aircraft sends out an emergency signal.
"The purpose of going up is to investigate what the situation is," he said. "Often when a Quick Reaction Alert aircraft is launched the details are not known, but it is known that a signal has been sent. Part of the purpose of sending a Typhoon up is to have a look and see what they can see."
The very same plane on the very same flight - from Lahore to Manchester - had been diverted to Stansted on September 7 2011 due to a bomb scare.
Essex Police said the plane, which had departed from Lahore, has landed at Stansted.
It is understood the incident happened around 10 minutes before the plane, flight number PK709, was due to land in Manchester at 2pm.
The Pakistan International Airlines plane that has been diverted from Manchester Airport to Stansted is carrying 297 passengers, Reuters reported.
Essex Police has confirmed the plane diverted to Stansted Airport has now landed:
The plane diverted to Stansted Airport has now landed at the airport. Police + partners are continuing to respond.From @EssexPoliceUK on Twitter:
Two RAF Typhoon jets are escorting a passenger plane from Pakistan to Stansted airport - the UK's designated counter terrorism airportFrom @chrisshipitv on Twitter:
The RAF has confirmed that one of its Typhoon jets was scrambled from RAF Coningsby in Lincolnshire in order to divert a passenger jet from Manchester Airport.
A Pakistan International Airlines passenger flight has been diverted from Manchester Airport to Stansted. No reason has been given so far.
This flight tracker appears to show flight PIA709 moving dramatically off its course and heading south towards London.
Essex Police said its officers are responding after "an incident" occurred on a plane:
An incident has occurred on an aircraft. Police + partners are responding + a further updated will be released asapFrom @EssexPoliceUK on Twitter:
No further details were given.
An RAF Typhoon jet has been launched to investigate an incident involving a civilian aircraft in UK airspace, the Ministry of Defence said today. Reports said the aircraft is a Pakistani passenger plane which has been diverted from Manchester to Stansted.
The aircraft, which is still in the air, is a Pakistan International Airlines passenger plane which was flying from Pakistan to Manchester, a Manchester Airport spokesman said.
Boris Johnson tweeted this picture of him with Hollywood legend Will Smith saying 'great to see Will Smith, @officialjaden & 90 kids at my Leadership Club achievement events today.'