In pictures: What caused the UK air traffic control failure?

Heathrow and Gatwick airports both experienced steep delays and cancellations

Last updated: August 29, 2023 | 10:52

Compiled by Nivetha Dayanand, Web Editor, with inputs from Reuters

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Air-traffic control services in the UK sought to restore normal operations after an hours-long system outage led to hundreds of delays and cancellations on one of the busiest days this travel season.

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The NATS authority said it had "identified and remedied" the technical issue that knocked out the automated flight planning system earlier on Monday.

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The system failure prevented planners from automatically processing flight plans and forced them instead to revert to manual input, meaning they couldn't manage the same volumes.

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Heathrow and Gatwick airports both experienced steep delays and cancellations, with chaotic scenes playing out at London's two main hubs as the number of axed flights swelled.

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The glitch coincided with one of the most active extended travel weekends, with the UK off on a national holiday on Monday and summer-vacation travelers returning back home.

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Some 3,049 flights were due to depart UK airports on Monday, with about the same amount arriving, according to aviation analytics firm Cirium.

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The failure occurred on a system that logs each aircraft's flight plan, which allows controllers monitoring flights to know where planes are headed and other important data, according to a statement by NATS.

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The separate technology the company uses to track aircraft positions appeared to be functioning.

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The issue had some similarities to a January 11 outage in the US that prompted a halt to all departures for a brief period and led to about 10,000 delays.

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In that case, a Federal Aviation Administration computer that logged safety alerts covering such things as runway closures was shut down after contractors damaged an underlying database.

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While the UK air space wasn't outright shut down, NATS said it has had to apply severe flow restrictions to maintain safety.

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Some international airlines were also affected, with Deutsche Lufthansa canceling flights from Frankfurt to Heathrow and Dutch carrier KLM circumnavigating the UK.

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