The collapse of air-traffic control that caused major flight chaos and how it unfolded

At 8.32am on 28 August 2023, French Bee flight BF731 was flying over the ocean between Artic Canada and the southern tip of Greenland on a routine journey from Los Angeles to Paris Orly airport.

The flight had taken them over the western US and eastern Canada. Ahead, according to the flight plan, lay Northern Ireland, Wales and England before crossing the Channel and making landfall above the pretty French resort of Deauville.

As was normal, a flight plan had been filed to Eurocontrol – the pan-European air-traffic control service based in Brussels. This online document – as all flight plans do – resembled a coded message. It began “ORCKA5 LAS Q70 BLIPP Q842 WINEN MLF J107 OCS CZI DIK DVL …”

The planned route is largely given as a list of “waypoints”: specific locations on the surface of the earth. Typically they have five-letter codes; BLIPP is northwest of Las Vegas. Flight plans also include navigational beacons, which have only three letters: DVL is the code for Devil’s Lake in North Dakota.

Coincidentally, it is also the code for the beacon located at Deauville in France.

The flight plan was in accordance with long-established standards. The pilots at the controls of the Airbus A350 jet had no reason to think there was anything unusual about the 5,867-mile journey from California to Paris.

But the computer system at Nats, the air-traffic control company responsible for planes flying through UK airspace, took a different view.

At 8.32am Eurocontrol routinely shared the plan with the relevant national air-navigation services so that they would be expecting the aircraft.

When the flight plan, containing duplicate codes for different beacons, reached the Nats HQ in Swanwick, Hampshire, it triggered a chain reaction that led to over 700,000 passengers facing disruption at one of the busiest times of the year.

The Civil Aviation Authority (CAA) established an independent review, which has now published its interim report. We now know more about how events unfolded, minute by minute.

All times British Summer Time.

Bank holiday Monday, 28 August 2023 4.59am French Bee flight BF731 departs from Los Angeles, destination Paris Orly. The airline, the pilots and the flight plan bear no responsibility for what happened next.

8.32am Flight plan for BF731 received by Nats from Eurocontrol. It referred to two beacons, both coded DVL. The…