It comes as the firm’s chief executive told MPs as many as 120 flights were cancelled and 500 delayed by an average of 45 minutes.
Apologising to ”customers, airports and the travelling public” for the computer glitch, Nats chief executive Richard Deakin said his company’s contingency and back-up plans worked well.
The company said: ”Nats confirms that there will be a financial consequence for the company from the delay caused by the technical problem at Swanwick on December 12 2014.
”Under the company’s regulatory performance regime, customers will receive a rebate on charges in the future.
”The amount is being calculated and will be notified to customers in due course.”
Appearing before the House of Commons transport committee, Deakin said around 10,000 passengers were affected by the Friday problem which occurred at Nats’ headquarters at Swanwick in Hampshire.
Heathrow, Luton and Gatwick airports were the ones mainly affected by the problem, Deakin said.
He told the committee: ”Any complex system will have failures”, adding that it would be ”unrealistic” to expect there would be no failures.
Deakin was appearing with Nats operations managing director Martin Rolfe as well as Andrew Haines, chief executive of the Civil Aviation Authority, which has already announced that an independent inquiry will be held into the failure.
The committee has already taken evidence this week from transport secretary Patrick McLoughlin who described the flight delays as ”unacceptable”.
Rolfe told MPs that the piece of equipment that failed last week dated from the mid-1990s and had dealt with 20 million flights and had been upgraded continually, The Telegraph reported.
Asked if he agreed with McLoughlin that the failure last week was ”unacceptable”, Deakin said: ”For the passengers who got caught up in all this, yes, it was unacceptable and by implication it was unacceptable for us as well.
”We are not proud of what happened. We are proud of how we responded.”
Asked about future performance, Deakin said: ”I can guarantee that this particular problem will not happen again but I cannot honestly sit here and say we will never have a computer glitch again.”
Sourced from Travel Weekly