An independent inquiry will be established into Friday’s air traffic control computer glitch which prompted chaos across UK airports.
The announcement from the Civil Aviation Authority came as it was confirmed that up to 10,000 passengers at Heathrow alone were affected.
Transport secretary Patrick McLoughlin said the failure was “unacceptable” but defended the National Air Traffic Services.
He told MPs he welcomed an inquiry by the CAA into the incident saying he hoped the findings would be available by March 2015.
Answering questions from the House of Commons transport committee, McLoughlin defended the overall performance of Nats, saying it was doing “an incredibly good job”.
“The average delay this year in Nats is 2.5 seconds per flight, whereas the rest of Europe we’re taking about 30 seconds,” he said.
He also compared the disruption to a telephone failure at the Swanwick air traffic centre in December 2013, which also caused flight disruption.
That incident caused 126,000 minutes of delays, compared to Friday’s 16,000 minutes, McLoughlin said.
The CAA is to appoint an independent chair to lead the inquiry, which will take evidence from experts on information technology and air traffic control.
However, transport committee chairman Louise Ellman questioned McLoughlin about the inquiry – which could involve CAA and Nats staff – saying it “did not look very independent,” the BBC reported.
The inquiry would be dealing with a very specialised and technical area, McLoughlin said. He said there was a limited number of people who could carry it out.
“We want to find out what went wrong and make sure it doesn’t happen again,” he added.
The regulator said: “The CAA will, in consultation with Nats, appoint an independent chair of the panel which will consist of Nats technical experts, a board member from the CAA and independent experts on information technology, air traffic management and operational resilience.”
It said the full terms of reference will be published following consultation with “interested parties including airlines and consumer groups”.
Nats chief executive Richard Deakin said the problem involved a computer code written a quarter of a century ago.
Deakin rejected criticism from business secretary Vince Cable, who accused the company of “skimping on large-scale investment” and being “penny wise and pound foolish”.
The company says it will be spending £575 million over the next five years on systems.