The Microsoft outage has caused the cancellation of 3,343 flights worldwide, according to an update at 3pm BST from aviation analytics firm Cirium, and the number is expected to keep rising.
The outage has affected the online check-in and reservations systems of a number of airlines, including Ryanair, American Airlines, British Airways, Kenya Airways, Delta Air Lines and Qantas.
American Airlines, Delta Air Lines and United airlines have grounded flights, while BA warned of disruption to some flights.
“Due to the widely-reported global Microsoft IT outage, some of our flights may experience disruption today. Our teams are working hard to manage the impact of this issue as quickly as possible,” it said.
Virgin Atlantic said its services were operating as scheduled.
Singapore Airlines said its service centre in Singapore and reservation hotlines are currently experiencing technical issues but there is currently no impact on SIA flights, which are operating as scheduled.
The outage has happened on the busiest day for UK flight departures this year, with over 3,214 departures alone – the highest number of daily departures since October 2019.
It said 52 flights have been cancelled departing UK airports so far, with a further 51 inbound arrivals cancelled.
Over the weekend – Friday 19 – Sunday 21 July – a total of 9,075 flights are scheduled to depart UK airports – equating to over 1.6 million seats, according to Cirium.
Ryanair said online booking and check-in are currently unavailable but told passengers to check in at the airport.
EasyJet said customers ‘should expect longer than usual airport queues’.
Air traffic control provider National Air Traffic Services (NATS) said it was unaffected by the IT outage.
“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,” it said.
The IT issues have also affected television channels, banks, supermarkets, train services and healthcare.
