Hundreds of flights to and from the UK have been delayed or cancelled after a breakage in the country’s air traffic control systems yesterday.

The systems are now up and running again but the knock-on effects could be felt for days, the controller NATS has warned.

Dozens more flight cancellations have been announced this morning from easyJet, British Airways (BA), Ryanair and other airlines.

The four-hour system failure caused travel misery for thousands of passengers trying to return home on the UK’s last bank holiday of the summer.

More than 1,500 flights due to arrive into or depart from the UK yesterday were cancelled, the latest data from aviation analytics firm Cirium reveals.

The breakdown has left aircraft and flight crew out of position for today’s schedule.

EasyJet has grounded more than 80 flights today, many from Gatwick Airport. While British Airways has axed more than 60 flights – mostly short-haul departures from Heathrow.

What caused the UK flight delays and cancellations?

The system failure was not caused by a cyber attack, the UK government confirmed this morning.

Transport Secretary Mark Harper said the problem was caused by a “technical fault” at flight control operator NATS (National Air Traffic Services).

The company said the outage had hit its ability to process flight plans automatically, meaning that for several hours the plans had to be input manually, a much slower process that meant fewer flights could take off and land.

“We have identified and remedied the technical issue affecting our flight planning system this morning,” NATS said in a statement released at 3.15pm UK local time yesterday.

“We are now working closely with airlines and airports to manage the flights affected as efficiently as possible. Our engineers will be carefully monitoring the system’s performance as we return to normal operations.”

“Our priority is ensuring every flight in the UK remains safe and doing everything we can to minimise the impact,” NATS added.

They apologised for the disruption and advised passengers to contact airlines for information on their flights.

Harper told the BBC that “it is going to take some days to get people back to where they should be.”

How are passengers being affected?

Passengers have taken to social media to express frustration at the lack of information on when or if their flights will depart.

Although the NATS technical issue is resolved, many planes and crews will now be in the wrong places so there will be ongoing issues with flight schedules.

One user reported being sat on the runway at Budapest airport for a flight to the UK and being told they may be delayed by 12 hours.

Another user posted from Pisa airport in Italy, saying their estimated departure time was 3.30am, a delay of 11 hours.

Should you still go to the airport?

Before leaving for the airport, check your airline’s app, website and social media channels for the latest advice.

You should also check the airport’s website departures or arrivals board for information.

Edinburgh airport, in Scotland, has advised passengers “not to come to the airport before checking with their airline on the status of their flight.”

For flights within Europe, you are advised not to arrive at the airport more than 2-3 hours before your flight to avoid overcrowding.

What is the advice from airlines?

Easyjet issued a notice to passengers saying their cancellations are “due to aircraft being out of base and yesterday’s delays having an impact on the safety regulated crew operating hours.

We notified customers in advance and provided the option to transfer their flight for free or receive a refund to help them rearrange their plans. We recommend that all passengers flying with us today continue to check the status of their flight on our Flight Tracker www.easyjet.com/en/flight-tracker for real time information before travelling to the airport.”

Ryanair have said that “more than 20 Ryanair aircraft were unable to get back to their home base last evening and a considerable number of our crews ran out of their legal duty hours limit yesterday.

“Today, Tues 29 Aug, passengers can expect some flight disruptions as we work to get our aircraft and crews back on schedule. We expect some flight cancellations and considerable flight delays today caused by this latest, still unexplained, NATS failure.”

British Airways have advised passengers due to fly with them today “please do not travel to the airport without checking the status of your flight, as it may be delayed or no longer be operating. You can do this by visiting Manage My Booking and checking your email inbox.

“Any customers due to travel with us on a short-haul service on Tuesday 29 August or Wednesday 30 August can move their flights free of charge to a later date, subject to availability. We are also rebooking customers onto alternative airlines where possible and have stood up additional colleagues in our call centres to assist our customers.”

Are you entitled to compensation due to air traffic control restrictions?

As a passenger, you have legal rights. The following advice applies to flights:

• departing from an airport in the UK on any airline

• arriving at an airport in the UK on an EU or UK airline

• arriving at an airport in the EU on a UK airline

If a delay or cancellation is not the airline’s fault, it is rare for passengers to be given financial compensation.

However, you are entitled to certain help for the duration of the delay.

What the airline must do if your flight is delayed

The UK’s Civil Aviation Authority (CAA) stipulates that if your flight is “significantly delayed” airlines must provide:

• A reasonable amount of food and drink (often provided in the form of vouchers)
• A means for you to communicate (often by refunding the cost of your calls)
• Accommodation, if you are re-routed the next day (usually in a nearby hotel)
• Transport to and from the accommodation (or your home, if you are able to return there)

The CAA explains that, “The airline must provide you with these items until it is able to fly you to your destination, no matter how long the delay lasts or what has caused it.”

If your flight is cancelled

If your flight is cancelled, you have the right to choose between a refund or a new flight. You will usually be asked which option you want to go for when the airline contacts you to say the flight is cancelled.

While you wait for your flight, for instance if you decide to wait at the airport for the next available flight, the airline must provide:

• A reasonable amount of food and drink (often provided in the form of vouchers)
• A means for you to communicate (often by refunding the cost of your calls)
• Accommodation, if you are re-routed the next day (usually in a nearby hotel)
• Transport to and from the accommodation (or your home, if you are able to return there)

The airline must provide you with these items until it is able to fly you to your destination, no matter how long the delay lasts or what has caused it.

For further details on compensation and passenger rights, check the CAA website.

Is it still safe to fly?

Travel expert Simon Calder told Sky News that the shutdown would not cause safety issues because the system was “designed to cope” with a shutdown and aircraft carried contingency fuel.

But he added: “This is of course one of the busiest days of the year. There are hundreds of thousands of people flying into the UK, frankly this is the last thing anyone needs.

“It will at the very least have caused enough disruption for the system to be in disarray for certainly until the end of the day and possibly for a few further days ahead.”

The travel expert said air traffic controllers at Heathrow – the UK’s busiest airport – be forced to reduce the frequency at which flights are able to land.

He explained: “Normally you have flights landing typically every 90 seconds or so. They can switch away from the digital system and become much more analogue, bringing the aircraft in more manually. However, you are not going to be able to do it at the same rate.

“For Heathrow and Gatwick in particular there is so little slack in the system that it can cause problems. If you’re reducing the flow rate coming in and keeping aircraft on the ground at those airports it will be a very difficult afternoon.”