British fighter jets scrambled to intercept a passenger plane after reports of an incident on a flight from Pakistan.
The plane was diverted and two passengers were arrested.
But British police say the incident is not being treated as terrorism.
Britain is on full alert two days after the brutal killing of a soldier on the streets of London, by men shouting Islamist slogans.
Anchor Marco Werman speaks with the BBC's Angus Crawford at the airport where the plane landed.