At 12:48 BST yesterday, Heathrow stopped every departure on the board. The cause was a fault in NATS’s flight-processing system — the software that turns a filed flight plan into a departure clearance — and it didn’t stop at Heathrow. Gatwick, Southend, and Jersey lost departures too, while arrivals kept landing the whole time. That’s the signature of this specific failure: planes could come in, they just couldn’t be cleared to leave.

If you’re reading this on September 9 wondering why your flight is still delayed or canceled a full day after NATS says the problem was fixed, you’re not imagining things. This isn’t a look back at what happened. It’s what to do about it while it’s still happening to you.

Quick Verdict

What failed	NATS flight-processing system, nationwide
Started	12:48 BST, Tuesday September 8, 2026
Airports hit hardest	Heathrow, Gatwick, Southend, Jersey (departures only — arrivals kept landing)
Fix applied	16:40 BST
NATS declared resolved	19:30 BST
Tuesday cancellations	1,300+ UK-wide (Flightradar24)
Wednesday cancellations (so far)	177, nearly all at Heathrow
Cause	Technical fault — cyberattack explicitly ruled out by NATS CEO Martin Rolfe
Cash compensation owed?	Almost certainly not, for the core NATS failure — treat this as an extraordinary circumstance
Still owed regardless	Rebooking or refund, plus meals and a hotel if you’re stuck overnight

What Actually Happened on Tuesday

NATS first confirmed a “technical issue” shortly after 13:00 BST on September 8, then narrowed it to a fault inside its flight-processing system by mid-afternoon. Engineers applied a fix at 16:40 BST. By 19:30, NATS said its systems were “operating normally” again. Under five hours, start to finish, for the actual outage.

Here’s the part that matters if you’re still stuck: NATS was clear from the start that recovery would take longer than the fix itself. Fixing the software doesn’t put every aircraft and crew back where they were supposed to be at 12:48 BST. That gap between “resolved” and “recovered” is where you are right now.

NATS CEO Martin Rolfe went on BBC Radio 4’s Today programme Wednesday morning and ruled out a cyberattack directly: “We have at this point ruled out cyber, we don’t believe it was a cyber attack.” He also said NATS hasn’t seen this specific failure mode before in 50 years of operation — which is a way of saying nobody yet has a clean answer for why it happened, only that it’s fixed for now.

The scale, per Flightradar24: 1,300 flights canceled to and from UK airports on Tuesday, with Heathrow alone accounting for 527 cancellations and 426 delays. Gatwick, Stansted, Luton, and London City all took real hits too.

Why It’s Still Hitting You on Wednesday

177 flights were already canceled by Wednesday, nearly all of them at Heathrow. That’s not a new failure — it’s the tail of Tuesday’s. Three things are stacking up against a fast recovery:

• Aircraft are in the wrong cities. A plane that should have flown London to Edinburgh and back Tuesday night is sitting in Edinburgh Wednesday morning instead, and something else was supposed to use that slot.
• Crews are out of position for the same reason, and pilots and cabin crew have hard legal limits on how many hours they can work in a stretch. An airline can’t just add another leg to fix the schedule — if a crew’s clock runs out, that flight cancels no matter how ready the aircraft is.
• Heathrow’s operating cap makes the math worse. The airport runs close to its coordinated slot limits on a normal day. There’s very little spare capacity to absorb a squeezed-together backlog, which is exactly why Wednesday’s cancellations are concentrated there.

This is the same pattern that dragged the Norway ATC strike’s disruption into a second day back in August — a controllers’ walkout ended, but the knock-on scheduling mess didn’t end with it. Ground-stop failures rarely resolve on the same clock as the fix.

Am I Owed Compensation for the NATS ATC Failure?

Work through it in order:

1. Was your flight departing from or via a UK airport on September 8 or 9? If yes, UK261 (the retained, post-Brexit version of EU261) applies regardless of which airline you flew.
2. Was the delay or cancellation caused by the NATS system failure specifically? If your airline cites “air traffic control restrictions” or a NATS-linked reason, that’s almost certainly going to be classified as an extraordinary circumstance — the same category that covers third-party ATC strikes.
3. Are you expecting £220–£520 in cash compensation? Don’t count on it for the core failure. UK261 exempts airlines from that tier when the cause is genuinely outside their control, and a national ATC provider’s software fault is about as outside-their-control as it gets.
4. Was your specific flight’s cancellation extended by something the airline could have controlled — an available aircraft that didn’t get used, or a crew that could have been repositioned but wasn’t? That’s a narrower case, but it’s the one place a compensation claim might actually hold up. Worth checking before you assume you have no claim at all.
5. Are you expecting a refund, rebooking, meals, or a hotel? Yes, unconditionally. None of that depends on whose fault the delay was.

What You’re Still Entitled To

Extraordinary circumstances kill the cash compensation tier. They don’t touch anything else. Airlines still owe you:

• A choice between a full refund and rebooking on the next available flight, if your flight is canceled.
• Meals and refreshments once you’ve been waiting more than two hours.
• Hotel accommodation and transport to it, if you’re stuck overnight because of a rebooking.

Airlines have been processing this at volume since Tuesday afternoon, which means gate agents are stretched and the instinct is to hand you a voucher and move to the next person in line. If you want a cash refund instead of a travel credit, say the word “refund” explicitly. Don’t accept a default.

Your Rebooking Action Plan for Today

1. Check your airline’s app first, before calling or queuing at a desk. British Airways, easyJet, and Ryanair have all been pushing rebooking options and waiver notices directly through their apps since Tuesday — that’s faster than any phone line right now.
2. If you’re rebooked onto a new routing, cross-check it against Google Flights before accepting. With this much schedule disruption, airlines are sometimes offering the first available seat rather than the fastest one.
3. If your flight isn’t canceled yet but you’d rather not risk it, ask about a free date change. With Heathrow absorbing most of Wednesday’s cancellations, moving a flexible booking off today entirely may beat waiting to see if yours gets pulled.
4. Keep every receipt for meals, hotels, and onward transport you pay out of pocket. Duty-of-care reimbursement claims move faster with documentation attached from the start, and airlines have historically been slow to proactively cover costs during multi-day disruptions like this one.
5. Check whether your credit card’s trip delay benefit applies, especially if the airline’s own duty-of-care response is slow to materialize at your gate. What Chase Sapphire, Amex Platinum, and Venture X actually pay out — and what documentation they require — is worth knowing before you’re standing in a terminal at midnight.
6. If you already paid out of pocket and the airline won’t budge, an EU261/UK261 claims app can chase the rebooking and duty-of-care obligations for you — though given the extraordinary-circumstances exemption here, don’t expect one of these to win you cash compensation on the core failure. What these apps actually deliver versus what they promise is worth reading before you sign away a cut of a claim you might not be entitled to anyway.
7. Build in extra connection buffer through the rest of the week. NATS says its system is fixed, but the backlog clearing at Heathrow specifically is the kind of thing that can bleed into a third day if a single bad-weather afternoon lands on top of it.

Not NATS’ First Time

This is the detail that’s fueling a lot of the anger online: NATS had a comparable flight-processing failure in August 2023 that snarled the network for a full day and cost the industry an estimated £100 million in total. That earlier meltdown led to reforms specifically meant to prevent a repeat. Those reforms haven’t held. A Swanwick radar-related fault disrupted flights again in July 2025, and early coverage is already calling Tuesday’s outage the third major Swanwick failure since the 2023 reforms went in — not a first test, a pattern. Ryanair’s chief operating officer has already called for Rolfe’s resignation over it, which tells you how this is landing with the airlines eating the cost, whatever the eventual root-cause report says.

If you want the fuller picture of how “who caused the disruption” changes what you’re legally owed, Spain’s ongoing 2026 ATC disruptions work through the same extraordinary-circumstances logic against a different cause. The underlying rule doesn’t change; only the story behind it does.

The Bottom Line

A software fault in NATS’s flight-processing system grounded departures at four UK airports for under five hours on Tuesday and is still canceling flights at Heathrow a day later, because fixing the system was never the hard part — repositioning every displaced aircraft and crew is. You’re not going to get €220-to-£520 cash compensation out of the core failure; this reads as a clean extraordinary-circumstances case. You are entitled to a real choice between rebooking and a refund, meals if you’re waiting, and a hotel if you’re stuck overnight. Ask for those explicitly, keep your receipts, and check Google Flights before you accept whatever routing the app hands you first.

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Details current as of September 9, 2026, based on NATS’s public statements and reporting from IBTimes UK and CNBC. Cancellation counts and recovery timelines are changing quickly — check directly with your airline and NATS.aero for live status before you travel.