Two men were arrested at Stansted Airport in Essex on suspicion of endangerment of an aircraft.
Airport capacity at some south-east England airports, including Luton and Stansted, is underused, according to a London Assembly report.
Stansted Airport expects over 220,000 passengers to pass through the terminal across the Easter bank holiday weekend.
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.
Essex Police say they 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.
Police and partners are continuing to respond
Stansted says passenger flights in and out of the Essex airport are operating normally.
It follows the arrival of a Pakistani International Airlines flight which was diverted from Manchester and escorted in by military jets.
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.
Eurocontrol, Europe's air navigation safety watchdog, said "significant" delays are expected at Stansted Airport following an "incident with a 777 declaring an emergency":
Stansted Airport has said that the diverted plane is in an isolated stand away from passenger areas.
It added that the airport is operating as normal.
A British security source has told Reuters news agency that early indications do not suggest that the plane is the subject of a terror attack.
It is understood the incident on board the Pakistan International Airlines flight PK709 happened around 10 minutes before the plane was due to land in Manchester at 2pm.
Two Typhoon jets from RAF Coningsby have been scrambled to escort a passenger airliner.
The Pakistan International Airways jet has been diverted to Stansted airport which is the UK's designated counter terrorism airport.
Defence sources cannot yet say why the jets were scrambled to assist. The RAF carries out around a dozen such missions each year.
The passenger aircraft has now landed at Stansted.