The Guardian says about 300 flights cancelled, RTÉ says 425, TheJournal.ie says around 200

The failure. Nats, which runs air traffic control for the UK, said at 1.46pm on Tuesday it was investigating a technical issue disrupting departures. It later placed the fault in its flight processing system. The Guardian says the fix went in at 4.40pm. TheJournal.ie says 4.45pm.

The totals do not match.

Arrivals. Heathrow first said arriving flights were not affected, and The Independent and The Irish Times carry that line. The Guardian and RTÉ carry a later Heathrow statement that the fault was "impacting arriving and departing flights across UK airports". Dublin cancelled 21 inbound.

Not settled. Which count is right, and when the day ended. Each figure is a snapshot from a different hour and none is final. The Irish Times, publishing at 4.58pm, still has engineers "working urgently"; The Guardian, half an hour later, has the fix in. We hold no count from Nats itself and nothing published after Tuesday evening.

What this is about. On Tuesday 8 September 2026, a fault in the system that runs UK air traffic control grounded planes across Britain for hours. The failure also stopped flights between Ireland and the UK.

Who runs the sky. Nats (National Air Traffic Services) handles air traffic control for the United Kingdom. It guides planes crossing UK airspace from control centres at Swanwick in Hampshire and Prestwick in Scotland. It also runs the control towers at many large airports. The Irish Times puts that at 15. Nats used to be part of the Civil Aviation Authority, the UK's aviation regulator. It was part-privatised in 2001, and the government kept a stake.

How it got here. The same kind of failure has happened before. On the August bank holiday of 2023, Nats's flight-planning system shut down after it could not process one flight plan. Controllers had to fall back on entering plans by hand, and thousands of flights were cancelled over several days. The regulator ordered an independent review. The Guardian calls Tuesday's failure the third incident in just over three years. Nats placed this one in its flight processing system.

Why Ireland is in it. Ireland runs its own airspace through a separate company, AirNav Ireland. But much of Dublin's traffic flies to and from British airports, so a UK failure cancels Irish flights too. That is why RTÉ, TheJournal.ie and The Irish Times counted Dublin separately.

What is at stake. Passengers want to know what they are owed. Under UK and EU rules, airlines must give stranded passengers care, such as meals and rebooking. But an air traffic control failure normally counts as outside the airline's control, so cash compensation is not usually owed. The Guardian reports that airlines are calling for an overhaul of air traffic control. Nats says it is working to clear the "backlog of flights", according to The Irish Times.

Where it stands. Tuesday's early counts disagreed. The Guardian's later report says more than 1,000 flights were cancelled by about 8pm on Tuesday. It adds that at least 177 flights scheduled for Wednesday had been cancelled, "nearly all at London Heathrow", according to Flightradar24. We do not hold Nats's own account of the cause or a final total.