The technical problem at air traffic control which caused thousands of flights to be canceled and flights to and from Britain delayed on Monday fixed and will not occur again, the head of the British National Air Traffic Service (NATS) said today.

Thousands of passengers were stranded overseas after 1,500 flights were canceled on Monday, while disruption to schedules continued on Tuesday. The fact that this is a peak season for travelers means that those affected are not offered alternative flights for days.

The CEO of NATS Martin Rolfe noted today that the technical problem was caused by a flight plan that was not “sufficiently standard”.

This problem has since been fixedhe underlined.

“We have worked incredibly hard since we restored the service on Monday to ensure this type of incident cannot happen again,” he told the BBC today.

Ryanair criticized NATS for not having a back-up system. Airlines are now scrambling to help get travelers back.

Rolf added that NATS is trying to help airlines.

“We are working incredibly closely with them to make sure we help them recover as quickly as they can and as efficiently as they can,” he concluded.

The head of the International Air Transport Association (IATA), Willie Walsh, also told the BBC today that the cost of the problem of this for airlines is likely to reach around £100 million (approximately 116 million euros).

More than 1,500 flights were canceled on Monday — a public holiday in parts of Britain and one of the busiest travel days as the school holidays draw to a close — when air traffic controllers were forced to manually enter flight plans after the technical issue that affected the ability to automatically process flight plans. This resulted in thousands of passengers being stranded at airports in Europe and beyond.