Two British airports, including the UK's largest air force base, have been forced to suspend flights after extreme temperatures caused issues with their runways.
The shutdowns come as Europe experiences an extreme heatwave, which has seen Britain endure its hottest day of the year on Monday, with temperatures topping 38C.
Luton airport, located north of London, said on Monday afternoon flights were suspended due to a "defect" on the runway.
"Following [Monday's] high temperatures, a surface defect was identified on the runway," the airport said on Twitter.
"Engineers were called immediately to site and repair works are currently in progress to resume operations as soon as possible."
Aerial footage broadcast on the BBC showed engineers working on a large rectangular section of the runway that appeared to have the top layer of tarmac removed.
The airport is the fifth busiest in the UK and serves as the base for budget airline Easyjet.
By 6pm local time (3am AEST) the airport said it had reopened to outbound flights, and later updated to say inbound flights had also resumed.
Earlier on Monday it was reported that Royal Air Force base Brize Norton in Oxfordshire had also stopped flights in and out after the runway became unsafe due to the heat, with Sky News reporting the runway had "melted".
The RAF did not elaborate on what issues the air base was experiencing but said aircraft were using alternative bases and operations were not being impact but the closure of Brize Norton.
"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," the RAF said via UK's Ministry of Defence.
"This means there is no impact on RAF operations."
The heat has also seen rail bosses urge people not to travel unless necessary, with rail networks hit by mass cancellations and London's Underground network imposing temporary speed restrictions on its trains.
Wales records its hottest ever temperature
Europe has been hit by extreme temperatures over the past week, while a jet stream vortex has sent a plume of hot air over the UK and forced authorities to issue the country's first-ever red extreme heat warning.
Monday saw temperatures reach 38.1C in Santon Downham in Suffolk in England, just short of the UK's hottest ever recorded temperature, when the mercury hit 38.7C at Cambridge's Botanic Garden on July 25 in 2019.
The UK's Met Office said provisional figures showed Wales recorded its hottest ever air temperature on Monday, with 37.1C being registered at Hawarden in Flintshire at 4pm.
That eclipses the previous record high of 35.2C which was recorded at Hawarden Bridge on August 2 in 1990.
Temperatures are expected to go even higher on Tuesday, with highs over 40C forecast for some parts of the UK, with the Met Office saying there is an 80 per cent chance that high could be reached this week.
Police have urged the public not to swim in open water to escape the heat, with two teenagers drowning after getting into trouble in waterways.
