A fresh outage at the UK’s air traffic control agency caused disruption to some flights on Monday, less than two weeks after a meltdown that grounded thousands of journeys. Dozens of flights were cancelled and others delayed after National Air Traffic Services (Nats) reported an equipment failure at its Prestwick control centre that guides aircraft over Scotland and parts of the Atlantic. British Airways cancelled some domestic flights, including between Edinburgh and London City airport, and warned passengers to expect delays. Easy Jet cancelled more than 20 services while KLM, one of the biggest airlines serving regional airports, also scrapped some flights from Manchester, Leeds, Belfast and Humberside. Ryanair said 140 of its flights had been delayed, adding that the latest outage showed Nats’ claims to have made improvements were “worthless”.

Shortly before 11am, Nats said that the fault had been fixed and that it was working with airlines to help them restore their schedules. The agency, which came under intense criticism after an outage threw the UK’s air traffic control system into chaos earlier this month, said that Monday’s issue originated at its operations in Scotland and was unrelated to the previous incident. But despite Nats resolving the fault, airlines warned of more cancellations throughout the day as delays led to congestion in the airspace. Transport secretary Heidi Alexander said that the disruption would be “deeply frustrating for passengers after the previous issue”.

Airports, including Manchester, Edinburgh and Glasgow, were showing long delays to some arrivals, and two said that operators had been forced to use paper slips to process flights taking off or landing, as the system reverted to manual flight processing. In response to the fault, flights through Scottish airspace were reduced by 60 per cent early on Monday, while those leaving parts of the UK to cross the north Atlantic were cut by 40 per cent, according to airspace monitor Eurocontrol. Eurocontrol said long delays were expected until at least 1pm. The latest failure strains relations with airlines even further, coming only days after a report showed that a meltdown this month was caused by ageing software. Easy Jet said: “A Nats air traffic control system failure in its Prestwick Centre is causing delays to flights with some unable to operate. This, once again, calls into question the resilience of Nats’ systems and demonstrates the need for firm actions to prevent these repeated failures.” BA said: “Yet another technical fault with Nats means some of our customers are likely to experience disruption to their travel plans today. This is disappointing, and whilst it is an issue that is entirely out of our control, we’re doing everything we can to limit the impact on customers and are keeping them updated.”