London Luton airport and the UK's largest air force base have halted flights amid extreme temperatures: 'The runway has melted'

• RAF Brize Norton halted flights on Monday after extreme heat "melted" the runway, Sky News reports.
• London's Luton airport also suspended flights due to a runway "surface defect" caused by the heat.

Britain's Brize Norton Air Force base and London Luton Airport halted flights on Monday as a dangerous heatwave hits the UK.

The Royal Air Force shut down operations at its Brize Norton base because the "runway has melted," as Sky News first reported.

On Friday, the UK declared a national emergency, warning of potentially record-breaking temperatures on July 18 and 19. For the first time, the country's national weather service has forecasted temperatures exceeding 104 degrees Fahrenheit. The UK's current record temperature is 101.6 degrees, recorded in Cambridge during the summer of 2019.

"During this period of extreme temperature flight safety remains the RAF's top priority, so aircraft are using alternative airfields in line with a long-established plan. This means there is no impact on RAF operations," The UK Ministry of Defence said in a statement on Twitter.

The ministry's press office did not immediately respond to Insider's request for comment.

Meanwhile, London's Luton Airport is also experiencing flight interruptions due to the hot weather.

"Following today's high temperatures, a surface defect was identified on the runway," the airport said in a statement on Twitter. "Engineers were called immediately to site and repair works are currently in progress to resume operations as soon as possible."

According to Flight Aware, 17% of flights departing from London Luton airport have been delayed thus far. London Luton Airport did not immediately respond to Insider's request for comment.

The Royal Air Force halted flights in and out of its Cranwell military base on Monday and Tuesday last week, a military source told Sky News, adding that tar has been sticking to RAF officials' boots and aircraft wheels since summer began.

Extremely hot weather has made this summer's flight chaos even worse. On top of runway damages, high temperatures can decrease the weight capacity of planes — forcing aircrafts to unload luggage and even passengers in order to safely take off.

One passenger told Insider that Air Canada "begged" 25 people to switch their flight after boarding in Denver because the plane was "too heavy" to take off in the triple-digit heat.