Flights at London’s Heathrow and Gatwick airports have been delayed for up to 11 hours as the heatwave turns to thunderstorms.

More than 800 flights have been delayed in and out of the two travel hubs so far on Saturday and dozens cancelled, many due to the stormy weather. The UK’s air traffic control service said delays were expected to continue for the rest of the day.

Some passengers have taken to social media to express their frustration, with one saying her daughter was stuck on an Easyjet plane at Gatwick for four hours before it was cancelled.

Gatwick told BBC News that temporary air traffic control restrictions had been put in place, while Easyjet apologised for the disruption.

More than 400 flights arriving at or departing from Heathrow have been delayed so far on Saturday, according to tracker FlightAware, and another 400 in and out of Gatwick.

Delays to affected flights vary, but Heathrow’s live arrival board shows a British Airways flight from Santiago, Chile that was due to land at 10:00 BST but is now not expected to arrive until 21:00 this evening.

Europe-wide aviation agency Eurocontrol mapping shows the most severe air traffic control delays in airspace between south-east England and north-western Europe, where the storm clouds are currently located.

However, other UK airports remain largely unaffected.

NATS, the UK’s air traffic control service, said “weather disruption was expected to continue through the rest of the day” after “forecasted severe weather across the south east of England”.

The thunderstorms developed overnight – bringing rain and lightning to parts of the UK – following a record-breaking heatwave, with the hottest ever June high of 37.3C recorded in Suffolk on Friday.

An amber warning for extreme heat is in place until Sunday morning for parts of eastern and south-east England – while the thunderstorm to the south of the UK is forecast to worsen throughout Saturday afternoon.

Eurocontrol said a “broad area of hot, unstable air” stretching from northern Spain to southern Sweden was likely to see further storm-cloud development overnight, adding that there was “a large degree of uncertainty” over when and where they would develop.

Flights are having to avoid the area with turbulent conditions, having a knock-on effect on schedules.

Passenger Adam Joseph, 29, told BBC News that he had been stranded at Venice airport in Italy without air conditioning because his flight to Gatwick had been delayed by four hours and counting.

He was due to depart Venice at 12:30 local time but said the plane had not yet left London on its outbound leg.

“We could’ve stayed at the hotel for another three to four hours,” Joseph said.

“We are also being told that even in the event of a four-hour-plus delay, because of an air traffic control restriction we will not be entitled to compensation.”

He added: “I’ve had to give up my chair to a family with a pregnant mother.

“People are very angry… we have had no communication from [BA] whatsoever.”

BA apologised for the inconvenience, adding: “Like other airlines, we’ve had to make some adjustments to our schedule today due to air traffic control restrictions caused by adverse weather conditions affecting parts of UK airspace.”

Gatwick confirmed some flights had been delayed and cancelled on Saturday “due to ongoing thunderstorms” and temporary air traffic restrictions.

Heathrow is advising passengers to check the status of their flight with airlines before travelling.

Meanwhile, one woman wrote to Easyjet on X on Saturday morning: “My daughter has been sat on a plane at Gatwick for 4 hours and now you’ve cancelled the flight. She’s on an Easyjet holiday. What should she do?”

Easyjet said that, with thunderstorms restricting the number of arrivals and departures, it has had to “pre-emptively cancel some flights to and from Gatwick in advance”.

It added that it was giving passengers options including refunds, rebookings, hotel accommodation and meals where required.