As of 5pm BST, flight schedule analyst Cirium confirmed nearly 4,300 flights had been cancelled globally – around 4% of all scheduled services on Friday. It also stressed this figure was likely to increase "as the day progresses".

Some 143 flights departing UK airports had been cancelled by 5pm (4.6% of all those scheduled), with a further 142 inbound services pulled. Reports from Spain suggest its entire airport network has been affected.

Jet2holidays said it is continuing to monitor the situation, but warned: "There may be operational disruption in some airports, including at check-in and boarding." 

It added that customers updated via its trade website. "Currently, all flights are due to depart as scheduled and our teams are present to assist customers," Jet2holidays said.

Which UK airports have been affected?

• At Edinburgh airport, the BBC reported early on Friday morning that the departure boards had frozen in the airport’s main terminal.
  
  
• Heathrow confirmed the outage had affected certain systems at the airport, but stressed flights were operating.
  
  
• Gatwick said it had been experiencing issues since early morning. "This is a global issue affecting some airlines’ check-in systems, baggage and security, including eGates," said a spokesperson.
  
  
• All Tui flights from Cardiff airport are delayed by at least an hour, according to the airport’s website, while Bristol airport reported "limited impact", but added: "We do expect some disruption later today."
  
  
• Manchester and Stansted airports revealed check-in and boarding were being carried out manually and confirmed the process was "taking longer than usual" for affected airlines. Similarly, East Midlands airport said some processes such as check-in and boarding were "being carried out manually and are taking longer than usual" It added that while most flights are unaffected, the terminal is busier than normal. Some retailers at the airport have also not been able unable to process credit card payments. All three airports are owned and operated by Manchester Airports Group.
  
  
• Birmingham airport also said there were "some" delays at check-in. "This is clearly a rapidly evolving situation," it added.
  
  
• Posting to Facebook, Newcastle airport said it is currently operating as normal and working to keep disruption to a minimum. It recommends travellers stay in touch with their airlines and to regularly check flight information online. One Facebook commenter, though, stated queues were "huge".
  
  
• Belfast International airport confirmed there was "disruption" across networks and advised passengers to check their flight status.
  
  
• Luton airport remains fully operational despite some airline and retail partner systems "being impacted by the global IT issue".
  
  
• Liverpool John Lennon airport has advised that some airlines have reverted to a "manual check-in process" but that flights are still operating as usual.

Elsewhere, Berlin airport has reported technical issues, while Sydney airport confirmed it was experiencing problems with departure boards going blank and at least one airline confirmed it could not check passengers in. Aircraft flying into Zurich airport are currently not allowed to land, according to reports.

The Department for Transport said it was aware of IT failures impacting several transport operators and terminals today. "We’re working at pace with industry and across government on the issue," it said. "There are no known security issues at present." 

But the UK’s air traffic control provider Nats posted on X: "The widely reported global IT outage impacting Microsoft products and services is not impacting any of Nats operational systems. 

"We are working closely with airports and airlines to understand how best we can support them and their customers. We advise passengers to check the status of their flight with their airline."

Friday (19 July) is set to be the busiest day for UK flight departures this year, with more than 3,214 flights alone – the highest number of daily departures since October 2019.

Airlines

Ryanair confirmed it had been affected and that passengers would be notified and kept updated. It is advising passengers to arrive at their departure airport at least three hours in advance.

"We regret any inconvenience caused to passengers by this third-party IT issue, which is outside of Ryanair’s control and affects all airlines operating across the network," the budget carrier added.

Elsewhere, United Airlines, Delta Air Lines and American Airlines have all issued “global ground stop” notices on all their flights.

German airline Lufthansa and Scandinavian carrier SAS also reported disruption to their booking systems. 

Eurowings said its online check-in is currently not working and Dutch airline KLM said that flight handling is currently "impossible" and it has "largely" had to suspend operations. 

"We realise that this is very inconvenient for our customers and staff, particularly in the middle of the summer holiday season," it added.

Aegean said while its operations were "relatively unaffected", issues with the "global chain and support systems" were impacting certain services and the airline’s website. It added: "Additionally, flights to airports whose operations have been impacted may be subject to changes."

Rail

Gatwick Express operator Govia Thameslink Railway, which also runs the Thameslink, Southern and Great Northern franchises, reported a "network-wide" IT issue.

"There are currently widespread IT issues across the entire network," it said. "This is due to a worldwide IT issue affecting multiple companies and industries." 

Ports 

The Port of Dover confirmed wait times were "slightly longer for check-ins" on Friday morning but added that this had been resolved. "Queue in the buffer zone is 40 minutes," it added. 

What exactly is going on?

Microsoft said it is taking "mitigation actions" after service issues and confirmed it was investigating problems with its cloud services in the US.

Other national and international media reports point to issues with the Crowdstrike security platform, which provides antivirus services.

‘Almost unprecedented’

Business Travel Association chief executive Clive Wratten said worldwide IT issues were having "a significant impact on global travel".

"Our travel management companies are working flat-out to find new arrangements and reassure passengers stuck around the world," said Wratten. "We will work with airlines, airports and train companies as the situation evolves."

Abta has urged travellers to "check both the information from your airline and your airport", while the Advantage Travel Partnership also told holidaymakers to arrive at airports earlier than normal to "avoid any further disruption". 

"Ultimately, the best way to protect yourself when it comes to facing travel disruption is to book with a local travel agent, someone you know you can easily contact and who will be readily available if you need support with your booking whether travelling for business or on holiday," said Advantage chief executive Julia Lo Bue-Said.

Rory Boland, editor of Which? Travel, called the situation "almost unprecedented". "Anyone with flights today will naturally be deeply concerned by the potential impact to their journeys," he said. 

He urged passengers to avoid checking in a bag as "queues... will be long and IT failures typically lead to lots of lost bags".  

More to follow.