RAF fighters escorted a Pakistani passenger plane to London on Friday after an incident on board the plane.
Pakistan International Airlines flight PK709 from Lahore to Manchester had 297 passengers on board.
The plane was diverted from Manchester airport to Stansted in London, just before it was due to land after an incident occurred on board.
One passenger told the BBC that the pilot informed them there had been threats.
Another passenger told Sky News that cabin crew had said two men had repeatedly tried to get into the cockpit and got into an argument with the cabin crew.
Two men on the plane were arrested by Essex police on suspicion of endangering an aircraft.
Stansted airport says the plane is isolated away from passenger areas.
Police are treating the incident as criminal rather than terrorism-related
Britain is on high alert after a soldier was hacked to death on a London street on Wednesday in what the government is treating as a terrorist incident.