A technical failure at National Air Traffic Services’ Swanwick control centre forced air-traffic controllers to halt departures across the United Kingdom on Wednesday, grounding flights at Heathrow, Gatwick, Stansted and other airports. Inbound aircraft were placed in holding patterns or diverted while controllers limited the number of planes entering London’s airspace to maintain safety. NATS said engineers identified the problem at around 16:05 BST and restored the affected system within roughly 20 minutes. The agency declared its systems “fully operational” shortly after 16:25 BST and apologised for the disruption. Transport Secretary Heidi Alexander confirmed the fault had been fixed but warned passengers to expect continued delays while airlines reposition aircraft and crew. The outage hit during the peak summer travel season and affected carriers nationwide. British Airways said the “vast majority” of its services were disrupted, and airports from Manchester to Edinburgh reported knock-on delays. While operations gradually resumed during the evening, airport operators cautioned that backlogs could persist for several hours.