An airport on the Hertfordshire border shut earlier today due to a runway defect caused by hot weather.

Passengers at London Luton Airport face delays or cancellations on all flights for the rest of today (Monday, July 18) after a portion of the runway melted during soaring temperatures.

The Bedfordshire runway, which sits next to the North Herts boundary, is one of two in the UK affected by extremely high temperatures. RAF Brize Norton in Oxfordshire was also forced shut due to the heat.

Official Met Office observations showed temperature readings at 36C at the Andrewsfield, Essex and Bedford weather stations - both near Hertfordshire - at 5pm.

An earlier London Luton Airport statement read: "Following high temperatures, a surface defect was identified on the runway.

"Engineers were called immediately to site and repair works are currently in progress to resume operations as soon as possible.

"We would like to apologise for the inconvenience caused."

WizzAir, Ryanair and easyJet flights were impacted by the runway closure, which began at around 4.15pm.

Flights to Dubrovnik, Alicante, Inverness, Jersey, Faro and Bucharest, among other destinations, were disrupted.

Departing flights resumed at 5.40pm. Arrivals resumed at 6.05pm.

An update from Luton Airport reads: "The runway re-opened to departing flights at 5.40pm. Arrivals remain suspended until further notice.

"We apologise for the inconvenience."

On Twitter, one passenger wrote: "EZY2368 waiting on the tarmac in Lisbon.

"Captain just announced that we are on the tarmac for at least two hours."

Another concerned social media user tweeted one airline operating out of Luton Airport. They said: "Can someone please contact me as a matter of urgency?

"I have two vulnerable adults stuck at Luton Airport after their flight was cancelled at the gate and no one to help them.

"They are over 100 miles from home. Disgusting service."

Earlier in the day, London Luton Airport staff urged passengers to prepare for the heat by keeping hydrated.

A tweet read: "With increasing temperatures today and tomorrow, don't forget to take an empty water bottle with you through security, to refill once you're through.

"You'll find water refill stations straight after security search and in the departure lounge."

As well as flight disruption, there are delays to Thameslink trains through Luton Airport Parkway.

A Thameslink spokesperson said: "Please expect delays of up to 20 minutes to services due to the speed restrictions in the area.

"Our Control Room staff are monitoring the issue.

"A reduced service is currently operating on this route to reduce delays to trains that are running."

According to Network Rail, passenger traffic on railways is down by around 20 per cent compared with last Monday.

On the RAF Brize Norton closure, an RAF spokesperson said: "During this period of extreme temperature flight safety remains our top priority, so aircraft are using alternative airfields in line with a long established plan.

"This means there is no impact on RAF operations."