Two men are being questioned on suspicion of endangering an aircraft after a plane was escorted to London by fighter jets.
The British nationals were led off the Pakistan International Airlines (PIA) plane by armed police officers, after it was diverted to Stansted Airport following a disturbance in the cabin.
Superintendent Darrin Tomkins of Essex Police confirmed a threat was made as the plane, flying from Lahore to Manchester with 297 passengers on board, was preparing to land.
According to Pakistan's Express News , one of the passengers claimed there were explosives on the plane, although Supt Tomkins said no suspicious items have been found.
"The cabin crew informed us that basically (the men) tried to come into the cockpit a few times," passenger Umari Nauman told Sky News.
"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."
Another passenger, Shahid Yaqoob, told Express News: "There was a conflict between two passengers after one of them got into a confrontation with the stewards.
"The two middle-aged passengers who previously had the altercation were simply asked to come with police who had boarded the aircraft. They were then handcuffed and taken away."
Zohaib Sattar was awaiting the arrival of his wife and father, who he spoke to on the phone shortly after the plane touched down at Stansted.
"They have taken two people off the plane and are checking the plane all over," he said. "My father said there was no warning or threat. All of a sudden, the plane just turned around."
RAF Typhoon fighter jets were scrambled when the plane, a Boeing 777, sent out an emergency code which alerted the Ministry of Defence and the police.
Flight PK709, which was due to land in Manchester at 1.30pm, was heading west towards the airport when it was suddenly re-routed near York.
Mashood Takwar, a spokesman for Pakistan International Airlines, said air traffic controllers in Manchester contacted the pilot 25 minutes before the plane was due to land, after receiving information from British security services.
The aircraft headed back out to the North Sea before travelling south to Stansted, escorted by Typhoon jets from RAF Coningsby in Lincolnshire.
Passengers were ordered to leave their possessions on board before leaving the plane, which was directed to an isolated stand.
Supt Tomkins said the two men arrested were aged 30 and 41 and would be questioned by detectives at a local police station.
"The plane will remain at its current location and will be subject to forensic investigation by specialist officers," he said.
Stansted, along with Glasgow Prestwick, is designated to deal with emergency situations such as terror threats and has specially-trained teams.
Flights to and from the airport continued to operate as normal.