Dozens of planes were diverted or delayed as Heathrow was forced to suspend arrivals due to a Royal Air Force flight, according to the airport.
A spokesman for the west London hub said the RAF's request for airspace closure was "unplanned".
The closure of airspace - which began at around 9am this morning - lasted for approximately 20 minutes.
At least four Heathrow-bound British Airways flights and one Virgin Atlantic aircraft were forced to land at other airports such as Gatwick, Stansted and Luton.
A spokesman for Heathrow said arrivals were paused briefly this morning due to an RAF request for an operational flight within part of Heathrow's airspace.
An RAF spokesman was not immediately able to identify an operation near Heathrow.
Councillors in Luton have dropped the town's bid to become the new UK City of Culture.Read the full story ›
A pedestrian has died after he was hit by a bus on the Luton to Dunstable busway.Read the full story ›
A Luton man who chased a car firing shots at it has been jailed. The 22-year old went on to shoot a man in the chest.Read the full story ›
A man cleared over a sword attack on police outside Buckingham Palace bragged to undercover officers that he had deceived the jury.Read the full story ›
Two teenage boys have been arrested in connection with a fire at a block of flats in Luton.Read the full story ›
Three people have been taken to hospital after fire broke out on the 14th floor of a block of flats in Luton.Read the full story ›
A man who burnt a woman with a cigarette during a seven-hour attack at a house in Luton has been jailed.Read the full story ›
The number of students dropping out of education has increased more at the University of Bedfordshire than anywhere else.Read the full story ›
A pedestrian has been seriously injured after being hit by a bus on the Luton to Dunstable busway.Read the full story ›