Thousands of people have been left stranded as disruption is expected to last into the weekend after a huge air traffic control meltdown.
Officials are investigating what was behind the blunder after almost 1,000 flights were grounded and cancelled with thousands more delayed.
Yesterday, Britain's National Air Traffic Services (NATS) experienced "technical issues" causing a knock-on effect today with 200 flights out of the UK cancelled and 200,000 people remaining stranded.
A French airline has been tipped as the cause of issue with one incorrectly filed travel plan.
Sources claim the fault could have been brought on by an incorrectly filed plan by a French airline
PA
Sources claim the fault could have been brought on by an incorrectly filed plan by a French airline.
Downing Street has not ruled out the possibility that the inputting error could have caused the disruption.
The travel chaos could last until Friday, with Britons being warned they could face "days of disruption".
NATS reportedly knows what caused the outage but are unaware of how it disabled the system.
A cyber attack has been ruled out by NATS.
The Prime Minister’s official spokesman said: "There’s going to be, think you’ll know that there’s going to be an investigation by the CAA (Civil Aviation Authority) and a report shared with Government.
"I think [Transport Secretary] Mark Harper confirmed this morning he’ll be getting that in days.
"I’m not going to pre-empt that. I’ve seen, obviously, various bits of speculation, but I’m not going to pre-empt the work that needs to be done."
But he added that experts had confirmed it was a "technical issue, not a cybersecurity incident".
The disruption for some Britons stranded overseas by the air traffic control issues in the UK could drag on into the weekend, Transport Secretary Mark Harper has suggested.
Asked if the problems could go on for longer than five days, the minister told GB News: "I think most people hopefully will be dealt with relatively promptly.
"There may well be people, a small number of people who are affected for longer."
He was due to meet with the airlines today to remind them of their duty to fly passengers home who have been left overseas.
Mr Harper denied a report that the problems had been caused by an incorrectly filed flight plan by French authorities.
"No, I don't know where that stories come from. We're looking into the, the root cause of it."TRAVEL LATEST:
Yesterday, Britain's National Air Traffic Services (NATS) experienced 'technical issues' - which has caused a knock-on effect today with 200 flights out of the UK cancelled and 200,000 people remain stranded
PA
When asked if officials would speak to counterparts across the English Channel, the spokesman said "you would expect them to be speaking regularly” with other countries “but I’m not aware of any specific conversations with French counterparts".
Transport Secretary Mark Harper said that despite the technical issue being resolved "flights are still unfortunately affected".
Home Secretary Suella Braverman added that passengers should contact airlines if they needed more information.