Airlines and airports warned of delays after a UK air traffic control glitch hit on Wednesday 30 July 2025

The technical problem caused major disruption as airports and airlines were working through a backlog of flights. The air traffic systems, which are run by NATS, were down for about 20 minutes.

Sharing his thoughts on the incident, Dr Junade Ali, an IET Fellow said: “The cause of this significant grounding of aircraft appears to be a technical issue at National Air Traffic Services (NATS). As of 16:25, NATS report a fix is being rolled out, meaning the issue was addressed promptly.

“In late 2023, there was a similar incident related to the IT systems that NATS uses. Given the short duration of the outage, it seems likely this is also an IT or software outage.

“NATS has previously thoroughly investigated such incidents and implemented suitable measures. From prior incident reports, the software is understood to not compromise safety at the expense of keeping airspace open.

"This is the right approach as, whilst keeping airspace open is important, the public risk appetite demands a high standard of safety when it comes to air travel. Incidents like this remind us of the need for robust IT systems that are resilient.” 

Brian Hoyle IET Fellow and Emeritus Professor of Electronic Sensors and Instrumentation at the University of Leeds added: “Critical comments of the recent "technical issue" reported by the UK National Air Traffic Service (NATS) have been extensive, as it obviously caused inconvenience for travellers. As examined by many correspondents about 100 flights were affected, corresponding to a short interruption of about 20mins. 

“Although not disclosed by NATS in detail, the likely issue probably arose from a hardware fault, or a significant data conflict, which caused the NATS Air Traffic Control (ATC) system to ‘stand-down’ triggering a progressive transfer of operations to its ‘standby system’.  The UK air traffic area is one of busiest in the world, with London Heathrow as having one of highest traffic levels, plus extensive transiting air traffic, e.g. routing from S Europe to North America (via the Great Circle - shortest distance) route. 

“As a pilot typically announces, cabin crew are mandated “primarily for our safety” in case of an emergency, as is the NATS ‘standby system’.  During the short 20min ‘switchover’ manual control of aircraft in flight may be necessary; and to ensure that the highest safety standards are maintained, flights scheduled for departure are simply delayed. 

“The ATC system is in reality a complex collection of computers, communication networks and information displays, with data feeds, including for example the well-known “ADS-B” ‘public’ broadcast of position, height and status from every aircraft in flight, about every second.  This system, originally mandated by the UN International Civil Aviation Organisation, is accessible, and used for example by information websites such as Flight Radar. 

“From a pragmatic summary of the engineering complexity, a 20min disruption is perhaps a very small price to pay to ensure that safe operations continue without any increase in risk, and so that normal levels of traffic can be quickly resumed.”

ENDS

Notes to Editors

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