The UK air traffic control glitch which caused thousands of flight cancellations and delays earlier this week is set to cost airlines around £100 million (€116m), IATA Director General Willie Walsh has said.
The CEO of NATS, the company which operates Britain's air traffic control systems, said the technical problem was caused by a flight plan which was "not sufficiently standard".
Martin Rolfe said the issue had since been fixed.
However, Mr Walsh said the explanation of the failure, which was released to the public does not make a lot of sense.
Speaking on RTÉ's Morning Ireland, Mr Walsh: "The only information I have is what has been released publicly, which I have to be honest, does not make an awful lot of sense. What they are saying is that there was an inaccurate data input into the system, which caused their primary and backup systems to shut down for safety reasons," he said.
He said if this is the cause behind the failure, he would be "staggered" as it would suggest there has been a weakness in their system for some time.
"We will wait to see what comes out of the full investigation, but clearly this is a fiasco, and it should never have happened," he stated.
Mr Walsh said safety should always come first, but the failure knocked out not just NATS's primary system but also the backup systems, and this was the unacceptable part.
He said he expected a detailed investigation in the UK involving the government, the CAA and NATS to establish what went wrong.
Mr Walsh said the incident would cost all airlines globally around £100m.
Thousands of passengers were stranded after 1,500 flights were cancelled on Monday and disruption to schedules persisted into yesterday. The peak holiday time period means those affected were not being offered alternative flights for days.
Airlines cancelled 20 flights into and out of Dublin Airport yesterday after cancelling 115 flights on Monday.
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This morning saw a full schedule of arrivals and flights at Dublin Airport, daa Media Relations Manager Graeme McQueen said, adding, that a "busy but normal day of operations" was expected.
Mr Rolfe said the technical problem was caused by a flight plan which was "not sufficiently standard", and the issue had since been fixed.
"We've worked incredibly hard since we restored the service back on Monday to make sure that this type of event can't happen again," he said.
Ryanair has criticised NATS for not having a back-up system. Airlines are now scrambling to help passengers return.
Mr Rolfe said NATS was trying to help the airlines.
"We are working incredibly closely with them to make sure that we help them recover as quickly as they possibly can, and as efficiently as they possibly can," he said.
Mr Walsh said airlines are frustrated that they cannot recoup any money lost due to the failure.
"NATS gets a free run here, they don't incur any costs as a result of this, and airlines are left to pick up the pieces and significant cost associated with the NATS failure."
He said it would take a couple of days for air travel to return to normal, but said he hoped things would be up and running again by the weekend.
Additional reporting: Reuters
