Second major air traffic control technical outage in two years disrupts UK airports

More than 150 flights into and out of UK airports were cancelled yesterday due to a technical issue which lasted for 20 minutes at the NATS Swanwick air traffic control centre. In a statement released at 16:06 on Wednesday 30 July, NATS said “As a result of a technical issue at NATS Swanwick air traffic control centre, we are limiting the number of aircraft flying in the London control area in order to ensure safety, which is always our first priority.”

The later updated the statement at 16:25 saying their engineers had restored the system and that normal operations were resuming. The final statement came at 17:10 when they stated “Our systems are fully operational and air traffic capacity is returning to normal. Departures at all airports have resumed and we are working with affected airlines and airports to clear the backlog safely. We apologise to everyone affected by this issue.”

Despite this, analysts are saying that delays to flights could continue for days due to a backlog of flights which has been created. The advice to passengers is to check with their airline and departure airport for advice. 

What have the effects been so far?

Data from Cirium reveals the true extent of the cancelled flights as of 10pm yesterday evening

Cirium Data correct as of 10pm on July 30. 

• 30 July 2025, has seen a total of 84 departures cancelled so far, across all UK airports – equating to 3% of all departures
• There has also been a total of 71 arrivals cancelled so far, across all UK airports – equating to 2% of all arrivals
• A number of inbound flights to UK airports were also diverted earlier today to European cities
• London Heathrow has seen the highest number of cancellations so far with a total of 29 departures and 17 arrivals so far.

As of 8:30am this morning, according to Cirium, 12 departures have been cancelled departing UK airports, with a further 11 arrivals cancelled today.

With the summer season in full swing, and Friday set to be the busiest day of the year for airports around the UK, this will likely exacerbate the effects of the outage. 

The outage comes only two years since the major failure of its flight planning system in August 2023 which saw hundreds of flights delayed and cancelled. The report for this was released in November 2024 and concluded that the technical issue had the biggest impact on aviation operations since the 2010 Icelandic volcanic eruption.

Dr Guy Gratton, Associate Professor of Aviation and the Environment, Cranfield University, said:

“National Air Traffic Services (NATS) have said there was a fault with their radar system, and this caused a stop on departing and arriving airline traffic on Wednesday afternoon for about an hour.  They control the upper airways of the UK from two sites – Swannick near Southampton, and Prestwick near Glasgow. It’s very integrated, and any interruption, as occurred, can only be solved in the short term by reducing the volume of traffic so as to make absolutely sure that in Britain’s very busy airways system, they achieve safe separation of all aircraft. As the systems come back up, they have to maintain that safe separation whilst introducing new traffic back into the airways system, so even a short delay will cause disruption for some time.

“It looks to me that NATS handled this very well, with departures and arrivals only stopped for about an hour.  There’s no sign that safety was compromised, and hopefully the overnight reduction in air traffic will give them a chance to clear the disruption and recommence flying on Thursday morning with only minimal residual delays. It’s inevitable that people directly affected are frustrated, but safety has to be the primary concern.”