The air travel disruption that hit the UK on the bank holiday is set to last for several days, Transport Secretary Mark Harper has warned.

"Lots of flights were cancelled and it is going to take some days to get people back to where they should be," he said to the BBC.

According to aviation analytics firm Cirium, 790 departures from British airports were cancelled yesterday - equivalent to about 27% of all departures. 

Some 785 arrivals were also cancelled, again equating to about 27%. 

Heathrow had the highest number of cancellations, followed by Gatwick and Manchester.

What happens if you miss your flight due to airport delays

What has caused the disruption?

The widespread disruption, which led to hundreds of flights being cancelled, was caused by a failure of air traffic control systems.

Issues began yesterday morning at the headquarters of the National Air Traffic Services (NATS) when its flight planning system failed. 

NATS was unable to automatically process the flight plans that are submitted by airlines - meaning they had to be inputted manually, causing delays. 

Officials haven't yet confirmed what caused the failure, however, government sources and aviation officials told The Times that a cyberattack has been ruled out. 

Sources also told the paper the issue could be due to an incorrectly filed plan by a French airline.

However, NATS has not commented on this. It is understood officials are aware of what caused the issue but not how it disabled the system. 

The outage has now been resolved, although it's likely to have a knock-on impact for days. 

National Air Traffic Services (NATS) said on Monday at 3.15pm that it had “identified and remedied” the technical issue, but later warned the ensuing disruption could last further into the week. NATS also said the failure would be investigated “very thoroughly”.

Are flights still being cancelled?

As airlines struggle to recover from the four-hour failure of the main air-traffic control system across the UK on Monday, airlines are making dozens more cancellations.

BA, easyJet, and Ryanair have grounded several flights on Tuesday following the severe travel disruption on the bank holiday due to the four-hour NATS outage.

Simon Calder told Sky News that "hundreds of thousands" of people will be flying into the UK today, adding that "disruption could last into the week".

He continued: "This is the last thing anybody needs", telling the broadcaster that planes would be touching down in places like Paris and Amsterdam instead of the UK.

"I'm afraid experience tells us something like this is not going to end quickly, it's going to be very messy."

He stressed that passengers would be safe and that contingency plans would be at play.

However, he warned: "If you're booked to fly into or out of the UK be prepared for serious disruption."