According to NATS, the issue was “radar-related” and it reduced flight traffic to ensure safety. It added there was no evidence the incident had been cyber-related.
The government said it was “working closely” with NATS to understand what had gone wrong.
Ryanair executive Neal McMahon said it was “outrageous that passengers were once again being hit with delays and disruption due to Martin Rolfe’s continued mismanagement” of NATS.
Referring to a previous incident two years ago, Mr McMahon said it was clear “no lessons” had been learnt and passengers continued to “suffer” as a result of Mr Rolfe’s “incompetence”.
In August 2023, more than 700,000 passengers were affected by the cancellation of more than 500 flights at the UK’s busiest airports due to a major outage.
EasyJet’s chief operating officer, David Morgan, said: “It’s extremely disappointing to see an ATC failure once again causing disruption to our customers at this busy and important time of year for travel.”
“We will want to understand from NATS what steps they are taking to ensure issues don’t continue,” he added.