Essex Police said the two men arrested on suspicion of endangerment of an aircraft have been taken to a police station to be interviewed:
2 men, aged 30 + 41, arrested on suspicion of endangerment of aircraft taken to police station for interview http://t.co/CH0qmyuubs
A relative of two PIA flight passengers said he spoke to his father on the phone after the plane landed at Stansted Airport.
Zohaib Sattar said his father Abdul told him there was "no warning or threat" before the flight was diverted.
Zohaib Sattar said: "They have taken two people off the plane and are checking the plane all over.
"The rest are just sat there waiting for further information.
"My father said there was no warning or threat, all of a sudden the plane just turned around".
A passenger told Pakistan's GEO TV that the two men arrested on board a Pakistan International Airlines plane had tried to move towards the cockpit during the flight.
Nauman Rizvi told the news channel that after the men were taken away by police, the flight crew told passengers there had been a terrorist threat and that the pilot had raised an alarm.
Another passenger, Umari Nauman, told Sky News, "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".
Ms Nauman said all the passengers had been ordered to leave their possessions on board before leaving the plane.
She also said helicopters escorted the aircraft before landing.
Pakistan International Airlines spokesman Mashood Tajwar said the airline had been unable to contact the pilot of flight PK709, despite repeated attempts.
Mr Tajwar said the control tower at Manchester Airport had received a call about a threat on board the plane and the advised the pilot to divert to its sister airport of Stansted.
Two RAF Typhoon jets are escorting a passenger plane from Pakistan to Stansted airport - the UK's designated counter terrorism airport.
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.
Two men were arrested at Stansted Airport in Essex on suspicion of endangerment of an aircraft after an RAF Typhoon jet was scrambled to escort a passenger plane travelling from Pakistan to the UK.
Police officers boarded Pakistan International Airlines flight PK709, which had been bound for Manchester, after it landed at Stansted and removed the men from the plane.
– Essex Police spokesman
"Essex Police have boarded a passenger plane diverted to Stansted Airport and two men have been arrested on suspicion of endangerment of an aircraft. They have been removed from the plane."
The RAF jet was scrambled following an incident around 10 minutes before the plane, which departed from Lahore, was due to land in Manchester at 2pm.
The incident is not thought to be terrorism-related at this stage, it is understood.
The Guardian reports that the pilot of the plane that has been diverted to Stansted Airport asked for this to happen because he was concerned about a disruptive passenger who had started shouting.
The pilot then became satisfied that the incident had been resolved, the newspaper reports.