Why 9 planes had to declare an emergency above one of Europe's busiest airports

Nine airplanes flying over London declared emergencies early Wednesday morning after an incident at one of Europe's busiest airports.

In total, 14 flights scheduled to land at London Gatwick Airport diverted to other airports between midnight and 1 a.m.

Gatwick is the UK's second-busiest airport and ranks 11th in Europe, having handled almost 43 million passengers last year.

Planespotters were briefly mystified as to why so many planes were broadcasting an emergency signal in the middle of the night, while many passengers returned from their vacations to a different part of England.

A London Gatwick spokesperson said the runway was temporarily closed "due to a technical issue with an aircraft."

" As a result, a small number of flights were diverted, with the majority later returning to London Gatwick," they added.

It therefore appears that the pilots declared emergencies due to low fuel, allowing them to receive priority landing at nearby airports.

The aircraft that stopped on the runway was a British Airways Airbus A320. It arrived from Palma de Mallorca, Spain, shortly after midnight, operating Flight 2673.

A person familiar with the situation said that this flight did not declare an emergency and was met by emergency services on the runway as a precaution.

It is not clear what issue the airplane may have had. Two flights scheduled to be operated by the aircraft on Wednesday have been canceled, according to data from Flightradar24.

"Our flight landed safely and customers disembarked normally following reports of a technical fault with the aircraft," a British Airways spokesperson told Business Insider.

Some airplanes were diverted as far as Bristol and Birmingham, about 100 miles away from Gatwick. Others landed at Luton and Stansted, on the opposite side of London.

Three of the 14 diverted flights did not continue on to Gatwick with passengers.

They included an easyJet flight from Rome that was stuck at Stansted because a refueling crew wasn't available. The BBC reported that passengers spent over two hours on the plane in the middle of the night before disembarking.

"While we worked to make onward arrangements for customers, as no ground handling staff were available for the unscheduled arrival, the aircraft was unable to refuel, and so customers disembarked in Stansted and were advised they would be reimbursed for their onward travel," an easyJet spokesperson told Business Insider.

"The safety and well-being of our customers and crew is our highest priority, and while this was outside of our control, we are very sorry for the inconvenience caused by the diversion and delay in disembarking."