An RAF Typhoon jet today escorted a passenger plane into Stansted Airport following an incident on board.
Two men were arrested at the airport on suspicion of endangerment of an aircraft, Essex Police said.
The Pakistan International Airlines plane was flying from Lahore, Pakistan, to Manchester when it was diverted to the Essex airport. It landed at approximately 2.20pm.
The incident is not thought to be terrorism-related at this stage, it is understood.
It is thought to have happened about 10 minutes before the plane, flight number PK709, was due to land in Manchester at 2pm.
An Essex Police spokesman said: “The plane has landed. We and our partner agencies are at the scene and dealing with the situation.”
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 Ministry of Defence spokesman said: “A Typhoon aircraft has been launched to investigate an incident involving a civilian aircraft within UK airspace.”
He added that the Typhoon is from RAF Coningsby in Lincolnshire.
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.
Today’s flight had left Lahore at 9.35am local time and was thought to have been carrying 297 passengers.