Airlines are demanding to be reimbursed for the cost of the August bank holiday air traffic control (ATC) failure.
Industry body Airlines UK said its members should not “carry the can every time we see disruption of this magnitude”.
National Air Traffic Services (Nats) said a technical glitch on August 28 prevented it from automatically processing flight plans, causing widespread disruption.
More than a quarter of flights to and from UK airports were cancelled that day, affecting around 250,000 people.
Cancellations continued for two more days as planes and crews were out of position.
Nats chief executive Martin Rolfe said one of the systems failed after it “didn’t process (a) flight plan properly”.
The plan submitted by the airline – which has not been named – was “not faulty”, he added.
In a preliminary report shared with Transport Secretary Mark Harper, Nats did not identify the route of a flight plan which led to the chaos but said the aircraft was scheduled to enter UK airspace during an 11-hour journey.
Airlines’ flight plans feature waypoints, which represent locations and are identified by a combination of letters and numbers.
The flight plan which caused last week’s disruption was submitted to Eurocontrol – which oversees ATC across Europe – before being passed on to Nats.
The process led to the plan featuring two waypoints around 4,000 nautical miles apart but with identical names.
This meant Nats’ software was unable to extract a valid UK portion of the flight plan and reacted by shutting down.
A back-up system followed the same steps and also stopped working.
Airlines cannot be the insurer of last resort ... and there must be accountability from Nats when things go wrong— Tim Alderslade, Airlines UK
Airlines UK chief executive Tim Alderslade said: “Airlines worked round the clock in response to the situation, providing accommodation to passengers and putting on more flights to bring them home as quickly as possible, at huge cost to all carriers impacted.
“Airlines cannot be the insurer of last resort though and there must be accountability from Nats when things go wrong.
“Airlines are seeking clarity on what options exist for Nats to cover our costs under the current legislation and will continue to engage with Government on all options for redress.
“We can’t have a situation whereby airlines carry the can every time we see disruption of this magnitude.”
Global airline body the International Air Transport Association (Iata) estimated the cost to airlines was nearly £100 million due to the requirement to provide affected passengers with alternative flights, food and drinks, and hotel accommodation.
Asked about the odds of the failure happening, Mr Rolfe said: “We know it’s at least one in 15 million, because we’ve had 15 million flight plans through this system and we can be absolutely certain that we’ve never seen this set of circumstances before.”
Nats said an “operating instruction” has been put in place to allow the “prompt recovery” of the system if there is a repeat of those circumstances.
A “permanent software change” to prevent it shutting down in such an event is expected to be implemented in the coming days.
Mr Rolfe added: “I’m very confident that the changes we’re making here will prevent this incident from happening ever again.”
The Civil Aviation Authority (CAA) announced it will launch an independent review into the meltdown.
Details of this will be published by the end of September and the inquiry is expected to take around three months.
