London: Two men were arrested on suspicion of endangering an aircraft after a Manchester-bound Pakistani passenger plane sounded a mid-air "security alert", forcing Britain to scramble two fighter jets to escort the plane to the country`s designated counter-terrorism airport here on Friday.
Two unidentified men are being held on suspicion of endangerment of an aircraft and they had been removed from the plane, Essex Police said.
Two Royal Air Force (RAF) fighter jets were deployed alongside the Boeing 777 to escort the Pakistan International Airlines flight travelling from Lahore as it was diverted to Stansted, Britain`s designated counter-terrorism airport.
"Typhoon aircraft from RAF Coningsby were launched today to investigate an incident involving a civilian aircraft within UK airspace; further details will be provided when known," a Ministry of Defence spokesperson said.
The MoD has since said that it is now a police matter and its involvement in the incident is over.
According to Essex Police, the men being held are aged 30 and 41 after its officers mounted the plane at Stansted.
Passengers said they had heard threats had been made on board, but there has not been any official confirmation of the exact nature of those threats.
A bomb disposal vehicle was seen by the plane. There were 297 passengers on board, besides 11 crew members, who were travelling from Lahore.
The plane was heading west towards Manchester when it was suddenly re-routed near York and headed back out to the North Sea, before travelling south to Stansted.
The airline has confirmed the diversion was for security reasons and the speculation so far is that it is a precautionary measure in response to an emergency signal.
The pilot, concerned about two disruptive passengers who had started shouting, asked Air Traffic Control to divert to Stansted as a precaution.
Their threats are believed to have been serious enough to call in RAF jets, which are in a constant state of readiness at the Coningsby, Lincolnshire, base in the east of England.
It is understood the incident is not being treated as a terrorist incident and that Essex police are not liaising with counter-terrorism officers at this point.
"We were about half-an-hour away from landing in Manchester and we saw that the plane was taking different actions. We did not know anything about it other than the pilots announced that they have landed at Stansted. And we landed, safely. Then he announced that he had a threat from someone, which was why he had landed the plane," a passenger told BBC.
Another passenger, Umari Nauman, told Sky News that cabin crew had added: "The cabin crew informed us that basically they tried to come into the cockpit a few times and because they had been asked not to do that, they got into a bit of an argument with the crew and made a few threats."
Manchester Airport said it expected passengers to be put on a coach from Stansted to Manchester later on Friday.
"A Pakistan International Airlines aircraft which was due to land at Manchester Airport at 13.30 BST today has been diverted to our sister airport London Stansted, where the authorities are investigating," an airport spokesperson said.