Director general Willie Walsh said the organisation has "crucial questions" to answer about their responsibility for the situation, which an investigation found was caused by incoming flight data.

"The failure of this essential service is unacceptable and brings into question the oversight of the Civil Aviation Authority (CAA) who are required to review the Nats resilience plan under the terms of its licence," he added.

Walsh raised concern that airlines will bear "significant" sums in care and assistance charges, on top of the costs of disruption to crew and aircraft schedules, but it will "cost Nats nothing".

"The UK’s policy makers should take note," he urged. "The passenger rights system needs to be rebalanced to be fair for all with effective incentives."

He continued: "Until that happens, I fear we will see a continuing failure to improve the reliability, cost efficiency, and environmental performance of air traffic control."

Transport secretary Mark Harper said airlines are "clear about their responsibilities" to their customers and it’s important passengers who have been affected get swift access to the refunds and support they are entitled to.

"I’ll continue to work closely with the Civil Aviation Authority to ensure that the process is working well," he added.