A military aircraft entering "spurious" flight data into the UK's air traffic control system led to an outage that grounded thousands of planes and threatens to topple the head of the agency. Four people briefed on Tuesday's incident said a flight plan submitted by a UK military aircraft triggered a series of events that led to the shutdown of Britain's skies for several hours. The entry caused a meltdown within the wider air traffic control system that took hours — and several attempts — to restart.

The incident has strained relations between carriers and National Air Traffic Services (Nats), the air traffic control agency owned by airlines and the government, and puts the future of its longtime chief executive, Martin Rolfe, in doubt. Transport secretary Heidi Alexander called Rolfe in for a meeting on Wednesday. Alexander said the outage was "not unavoidable" and demanded a review by Nats within a week.

While he can only be fired by the Nats board, led by former Rolls-Royce boss Warren East, the government owns 49 per cent and can withdraw its support. The Civil Aviation Authority will carry out its own independent investigation, reporting in six months, but next week's report from Nats is seen as crucial for Rolfe.

Airlines are particularly incensed because they were promised that a Nats failure in 2023, caused by a rogue flight plan, could never happen again.