Did blunder by French airline spark air traffic meltdown? Officials probe if a ... trends now

Officials are probing whether a single badly filed travel plan by a French airline was behind today's air traffic control meltdown which resulted in thousands of cancelled flights during the worst outage in more than a decade.

Experts have warned that disruption is set to continue into the week despite the 'network failure' that left thousands of holidaymakers stranded being 'remedied' on Monday afternoon.

Almost 1,000 flights were grounded and cancelled with several more delayed after Britain's National Air Traffic Services (NATS) said it experienced 'technical issues'.  The mayhem happened on one of the busiest days of the year, when more than a million people were due to fly out of or land in the UK.

In an extraordinary twist to today's fiasco, sources have told The Times that the fault may have been caused by an incorrectly filed plan by a French airline. MailOnline has contacted NATS for comment.

Passengers have been warned that they could face 'days of disruptions', which could last until Friday. An easyJet pilot told passengers he had never seen a failure on this scale in 20 years of flying.

It's understood officials are aware of what caused the outage but not how it disabled the system. A cyber attack was also ruled out by NATS. 

Cirium reported that more than 500 flights were cancelled by mid-afternoon, with hundreds more also aborted from knock-on effects. 

The data analysts also said that 3,054 flights were due to arrive into UK airports on Monday, which is around 543,000 seats. Another 3,049 flights (540,000 seats), were due to depart, meaning more than a million people were set to leave or arrive in the UK. 

*Are you affected by the UK air traffic control shutdown? Email your story, with photos, to [email protected] and [email protected] 

It follows a 'huge failure' of the national air traffic control system which caused chaos on the August Bank Holiday Monday.

Britain's National Air Traffic Services (NATS) said it experienced 'technical issues' that forced controllers to switch from an automatic system for landing and dispatching flights to a manual one. 

'Flight plans are being input manually which means we cannot process them at the same volume, hence we have applied traffic flow restrictions,' NATS said. A spokesman told MailOnline there was 'nothing to suggest a cyber attack'. 

NATS said at 3.15pm it had 'identified and remedied' the technical issue affecting air traffic control systems and is working with airlines and airports to support the flights affected. 

Transport Secretary Mark Harper said that despite the technical issue being resolved 'flights are still unfortunately affected'.

He tweeted that he would 'encourage all passengers to read the UK Civil Aviation Authority's guidance & be aware of their rights when flights are delayed or cancelled'.

Home Secretary Suella Braverman told passengers to contact airlines if they needed more information. 

At 1.45pm, the majority (78%) of flights leaving Heathrow were delayed, according to Flight Radar data, compared to 74% at Gatwick, 81% at Manchester and 86% at Bristol. 

Heathrow has urged passengers only to travel to the airport if flights are 'confirmed to be operating', adding: 'Schedules still remain significantly disrupted.' Delays at 11pm tonight were down to 59 per cent at Europe's busiest airport.

Under UK law, those affected have legal rights which oblige the airlines to provide support to customers flying from a UK airport, arriving in the country on an EU or UK airline, or arriving at an EU airport on a UK airline.

The Civil Aviation Authority (CAA) website says that in the case of a 'significant delay', the airline must provide a reasonable amount of food and drink, commonly in the form of vouchers, refunds for the cost of calls, and accommodation for passengers stuck overnight and transport to a hotel or their home.

The CAA accepts airlines are sometimes unable to organise such support, so passengers should make their own 'reasonable' arrangements and keep receipts to claim money back, but the authority adds that 'luxury hotels and alcohol' are unlikely to be paid for.

The authority adds that once a passenger accepts a refund or to travel later than the first available flight, then the airline is not obliged to provide food, drink or accommodation.

Britons returning from Tenerife told MailOnline they had been told to expect a wait of at least 12 hours.

Michele Robson, who used to work in air traffic control, said that it was 'unusual' for failures to last this long. As a result, 'nobody really knows at this point how long it's going to take,' she told BBC Radio 4. 

Ms Robson told the World at One programme: 'There was a flight planning system failure this morning which affected both centres in the UK.'

Speaking from Jersey Airport while waiting to fly to London, she said: 'Now they have enough data for four hours for controllers to work normally. After that point, they have to go manual which means that they work at a much slower rate so they can handle far less aircraft.

'So it looks like there's been what they would call a zero rate put on, where it means that no aircraft can take off inbound to the UK or probably outbound. It would generally be them trying to land things that were already in the air.

'So at the moment, we're just sitting here with no definite takeoff time.'

Contagion from the issue has already spread across Europe, causing delays for some flights leaving the Continent for the USA. 

TV presenter Gabby Logan said she has been left stranded on the runway at Budapest Airport while returning from the World Athletics Championships. She wrote: 'After almost 3 weeks away from home I am hours from hugging my family. And have just been told UK airspace is shut. We could be here for 12 hours. So we sit on the plane and wait.' 

The Liberal Democrats called on the Prime Minister to convene a Cobra meeting over the issue 

Transport spokesperson Wera Hobhouse said: 'Rishi Sunak and his ministers need to get a grip on this issue urgently and hold a Cobra meeting.

'Millions of holidaymakers could be facing huge disruption in the coming days due to this fault and we can't risk this Government being missing in action yet again.

'Brits need to know that the Government is doing all it can to make sure people aren't hit with major delays and disruptions in the coming days.'

Travel expert Simon Calder warned the situation would be 'miserable'. 

'There is very little slack in the system and there are hundreds of planes up in the sky heading to the UK,' he told Sky News. 

'What's going to happen to those aircraft, will some of them get down if they are in the vicinity of the airfield. 

'Otherwise you will see planes held on the ground in places like Amsterdam or otherwise being diverted if they're on a longer flight. That would typically be to a continental airport or an Irish airport.' 

Mr Calder said the shutdown would not cause safety issues because the system was 'designed to cope' with a

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