Major flooding at Heathrow Airport this morning has caused disruptions during one of the busiest travel periods of the year.

Terminals 2 and 3 have been flooded with the airport announcing access to the terminals has been restricted.

Heathrow warned passengers to allow extra time to get to the airport. It said in a statement on Saturday morning those coming to the airport should not travel by car to Terminals 2 and 3, encouraging them to arrive by train or use the Tube instead.

Those who need to drive should use Park and Ride, go to Terminals 4 or 5 and take the free train service.

The airport said in a statement: “Passengers travelling to or from either of these terminals today must not travel by road.

“Passengers are strongly advised to use Heathrow Express, Elizabeth Line and Piccadilly Line rail services where possible.

“Any passengers that must travel by car must use Park and Ride, head to Terminals 4 or 5 and take free rail services from there, or change at local rail stations.

“Please allow extra time for your journeys. Our teams are working to resolve the situation as quickly as possible, we apologise for any disruption caused.”

The flooding was caused by a main leak beneath Inner Ring Road West, which continues to impact road operations in the Central Terminal Area.

The flooding comes during peak school holiday travelwhen thousands of people fly from the UK’s largest airport every day.

Heathrow recorded its busiest day of the year so far on July 19 when 267,000 people passed through its gates.

Last week, Heathrow temporarily closed its Southern Runway after a grass fire broke out right next to it. A hectare of land was destroyed by the blaze.

The airport has recently revived its expansion plans to build a third runway. The government launched a public consultation in June on the proposals.

UK transport infrastucture under stress

While the cause of the flooding has not been revealed, the prolonged heatwave has impacted transport infrastructure across the country.

A Greater Anglia train derailed south of Wickford station in Essex on Friday less than 24 hours after 20 people suffered injuries after a Southern service derailed in East Sussex.

On Thursday, a Southern train carrying 150 people left the tracks around 3.54pm between Haywards Heath and Lewes.

This comes after experts told The i Paper that the Government may have to spend more upgrading infrastructure to help the network adapt to the changing climate.

While the cause of the two derailments has not been confirmed, heat expansion causing rail lines to buckle is one possibility that will be looked at by investigators, said industry experts.

The nation’s network operator pointed out that train speed restrictions are needed in hot weather to reduce the impact on the lines. It can mean fewer trains to avoid lines become overcrowded.

Phil Blythe CBE, professor of intelligent transport systems at Newcastle University, said it could take “a decade or more” to adapt the UK’s rail infrastructure to extreme heat, he said.

The nation’s network operator also pointed out that train speed restrictions are needed in hot weather to reduce the impact on the lines. It can mean fewer trains to avoid lines become overcrowded.

Passengers could face both “slower trains and reduced service” in the summers ahead “until a lot of these improvements can be made”, said Prof Blythe.