This article is more than 1 year old

This article is more than 1 year old

Rail and air passengers have faced another day of disruption due to the outgoing heatwave, as engineers struggled to repair damaged rail lines and air traffic control problems disrupted flights.

On the railways, passengers travelling on Great Northern, Thameslink and East Midland Trains were all advised to avoid travelling unless their journey was essential.

At Britain’s two biggest airports, Heathrow and Gatwick, thunderstorms and persistent hot weather in Europe delayed morning flights, while a technical glitch at the main air traffic control centre contributed to delays.

UK railways in chaos as searing heat sparks fear of derailed trains Read more

Fears that Thursday’s scorching temperatures could have buckled tracks led to speed restrictions on the railway, and overhead wires were also damaged. On Friday half of Thameslink’s lines were unavailable, while East Midlands trains between Sheffield, Nottingham, Derby and London St Pancras International were also affected. Network Rail said it had been unable to fix the damage to the overhead wires and would need to resume repairs on Friday night.

The ongoing problems came after thousands of passengers were left stranded at major stations on Thursday, the hottest July day on record, as temperatures of up to 38.1C (100.6F) created havoc for some train operators.

Facebook Twitter Pinterest The information board at London St Pancras did not make happy reading this morning. Photograph: Georgina Stubbs/PA

One of the worst-affected routes was the east coast mainline running from London to Edinburgh. One passenger posted a video onboard a stationary London North Eastern Railway (LNER) service showing sweat-soaked commuters, including a man with a baby, desperately fanning themselves.

Quick guide Why does hot weather disrupt UK railways? Show Hide How does hot weather affect UK trains? The temperature of steel rails can climb 20 degrees higher than the air around them. So when temperatures are approaching 40 degrees, track temperatures can come close to 60 degrees. That causes the metal to expand, putting it at risk of buckling. Overhead electrical lines can also expand and sag, putting them at risk of being pulled down by trains. A third problem is that dry weather causes cracks, or even potholes, in the ground beneath the track. Trains travelling over such sections have to move more slowly for safety reasons. Why do trains seem to run OK in hotter countries? When Network Rail stress-tests its steel rail for its reaction to heat, it does so based on the mean summer track temperature in the UK, which is 27 degrees. In parts of Europe, and other hot countries, they assume much higher temperatures and manage their track accordingly. Network Rail says it would not be cost-effective to build the UK’s tracks in the way they do in hotter countries because we don’t usually experience large variations in temperature. What is being done to reduce problems? The only way that Network Rail and train operators can respond is by imposing drastic speed restrictions, or cancelling services altogether, to avoid the risk of a train derailing from the misshapen track. Will the climate crisis cause more problems in future? As the world heats up, it is highly likely that the UK will experience more record-breaking heatwaves, meaning periods of rail disruption will become more frequent unless action is taken. Network Rail published its strategy for coping with the climate crisis in 2017. Among the questions it is considering is whether it might eventually become more cost-effective to spend money now on track capable of dealing with the heat, to avoid mounting costs of repairs and compensation for affected passengers. Rob Davies

Another image showed a man who had collapsed being treated by medical staff outside the train.

Apologising to commuters for delays and cancellations, Phil James, from Network Rail, said: “The extreme temperatures made travelling by train very difficult at times and we thank passengers for their patience while we worked hard to get people moving again.

“Everything was done to keep trains moving where possible, and last night hundreds of staff were out fixing the damage and repairing the railway ready for today.”

Passengers using Eurostar services to and from Paris were also facing severe disruption due to overhead power line problems in the French capital, the operating company said.

Although much cooler weather swept across the country on Friday, thunderstorms caused fresh difficulties for air passengers. British Airways announced that severe thunderstorms were causing significant delays and cancellations to flights in and out of London.

Heathrow airport also apologised after “extreme weather conditions across Europe” caused flight cancellations and delays.

A glitch at air traffic controllers Nats also contributed to delays at Heathrow and Gatwick, according to Eurocontrol, the European airspace monitor.

Facebook Twitter Pinterest Queues at Heathrow on Friday. Photograph: Steve Parsons/PA

Nats said: “We have a technical problem with a system at the Swanwick Air Traffic Control, which is causing some flight restrictions. We are doing all we can to fix it as soon as possible.”

Gatwick said departures were suffering an average delay of 38 minutes, due to a combination of the heat in Europe and the air traffic control issues. A spokesperson said: “Flights continue to arrive and depart from Gatwick however Nats has an issue with one of its radars and has put limits on the number of flights that can use Gatwick and other London airports. Passengers are advised to check the latest on their flight with their airline.”

Heathrow said: “Flights are currently arriving and departing at Heathrow, and we are supporting Nats to resolve the issue as quickly as possible. We apologise to passengers for any disruption that occurs as a result.”

The Met Office predicted that thunderstorms, which brought heavy rain, gusty winds and lightning in the south-east of England on Friday morning, could continue intermittently through the day.

Along Scotland’s Moray Firth coastline, temperatures will range from 25C to 27C, while in the south-east and East Anglia the mercury could rise to 31C.

The Met Office said a new record temperature for the month was set at 38.1C in Cambridge on Thursday afternoon, beating the previous record of 36.7C set in Heathrow in 2015.

The UK will see a return to more familiar conditions this weekend, as the weather becomes less settled; there is a high chance of rain for many eastern and north-eastern areas.

The government’s advisory committee on climate change has warned that the UK is not prepared for the expected increase in heatwaves due to the climate emergency.