Nats said in a statement: "We are doing all we can to fix it as soon as possible".
"Anyone due to fly in the morning is urged to check with their airline for the status of their flight before travelling to London Stansted Airport".
"Due to extreme weather conditions across Europe this evening, Heathrow and other airports are experiencing delays and cancellations to flights".
British Airways said it had been affected by severe weather conditions overnight as well as by the technical issue.
"Passengers should contact their airline for the latest information about their flight".
Lynn Morrison, a passenger at Heathrow Airport, took to social media to share an image of the crowded airport, describing the conditions as "chaos".
Heathrow also said that a number of flights had been delayed or cancelled but did not confirm how many planes had been grounded.
US economy grew more slowly in 2018 than previously thought
For the first quarter of 2019, real GDP is estimated to have increased 3.1 percent (table 1), the same as previously published. Economists also noted that business capital investment fell in the April-June quarter for the first time in three years.
Watch freakish incident that got Rowe and Martin expelled
Rowe and Martin were both later thrown off the race as it emerged there had been a little more than simple jostling. Speaking on ITV4, Thomas said it was the job of such riders to get their team's star men into strong positions.
Pictures posted on Twitter showed enormous queues of stranded passengers building up at Heathrow on Friday morning.
Alana Gomez, spokeswoman for travel comparison website Jet Cost, said: "Whilst passengers are justifiably aggrieved by the lengthy delays, they must understand that in these situations the safety of the passengers and crew is paramount, and the conditions felt yesterday made it unsafe to fly". Twitter/@lynn_morrison66Long queues could be seen around Heathrow airport as passengers waited for updates on their flights.
Donna Graham tweeted: 'There are hundreds of people queuing at Heathrow.
It comes after the Met Office yesterday issued weather warnings for large swathes of the country, stretching south-east across the midlands and as far north as Scotland.
"The thunderstorms could continue on and off through the course of the day", Met Office meteorologist Greg Dewhurst told PA.
Thursday was the hottest July day on record, with the 38.1C (100.6F) in Cambridge beating the previous record of 36.7C (98.1F) set in Heathrow four years ago.
New high-temperature records have also been set in parts of Belgium, Germany and Holland as a heatwave grips western and central Europe, pushing above 40C.
Naomi Smith, CEO of anti-Brexit group Best For Britain, said: "Johnson doesn't want what's best for Britain, but for himself". Mr Johnson promised British "children and grandchildren will be living longer, happier, healthier, wealthier lives".
Another surveillance video from a market about eight minutes away from Sardis Lake shows Kostial and Theesfeld together. Theesfeld's father, Daniel Theesfeld , a doctor in Texas, said in a statement to WMC that his son was innocent.
Last week, Mr Trump spoke to Mr Macron as he about the country's proposed digital services tax, the White House said. Chinese, German, Spanish and British firms are also affected, as well as the French online advertising firm Criteo.
The toddler then attempts to crawl and climb over the baggage on the conveyor belt to get back to his mother. When he finally descends into a room with staff, they rush over and lift him from the conveyor.
Imran Khan flew to the United States on a commercial flight instead of a private jet - reportedly to cut expenses. Prime Minister Imran Khan made the comment at the White House this week while meeting with President Trump.
Well, according to the boss of Marvel , it's time to put those hankies away as a fifth movie is already in the works. During the San Diego Comic-Con, Feige explained that the superhero will not be the same squad we've seen so far.
MSNBC host Rachel Maddow dedicated significant airtime to a theory that Trump's campaign colluded with Russian Federation . Former MSNBC co-host Krystal Ball attends an event in New York City on April 22, 2013.
But immigrant advocates and outside experts have warned that Guatemala does not meet the legal definitions of a "safe" country. Torres, the only member of Congress born in Guatemala, declared the agreement "ridiculous".
She assured him she "wouldn't want to be on this date with anyone else", as she landed her final dig at Michael. This new picture - shared by Amber Gill 's team on social media - will definitely surprise you, too.
His distinctive auto with its gold trim was seen left in the middle of Golders Green Road with the driver's door left open. Ozil , his wife and Kolasinac then fled inside a Turkish restaurant on Golders Green where they are regulars.
Canadian police confirm sightings of murder suspects
Police are encouraging the public to reach out with any information they may have before sharing possible tips on social media. Many of Gillam's residents are hydroelectricity workers employed at one of the three large nearby generating stations.
UK PM Johnson tells Germany's Merkel: The backstop has to go
In the coming days he'll speak on other aspects of a packed domestic agenda that looks suspiciously like an election platform. It's nearly certain that opposition lawmakers will try to topple Johnson's government in a vote of no-confidence in September.
Once Upon A Time Actor Gabe Khouth Dies At 46
Kelamis shared that Khouth was riding his motorcycle when he suffered a cardiac arrest , and "died as a result". Gabe Khouth , perhaps best known for his role as Sneezy/Tom Clark on ABC's Once Upon a Time , has died.
Apple won't get special treatment for Mac Pro parts
The company has not specified a release date for the Mac Pro beyond saying it will be available to order in the fall. Experts said there was little chance that Trump's tweets would have any impact on the company's investment in China.
AIA extends Tottenham sponsorship until 2027
Spurs finally moved into a new 62,000 seater stadium, which British media said cost one billion pounds, towards the end of last season on the site of their old White Hart Lane ground and have invested in a state-of-the-art training centre.