'One in 15 million' air-traffic chaos in UK was caused by a small software error. Here's what happened

A 'one in 15 million' event, as described UK's air traffic control provider NATS, caused the air traffic meltdown last week. The chief of NATS cited a flight plan with two identically named markers as reason for the air-traffic chaos.

On August 28, 1500 flights were cancelled as a result of which thousands of passengers were stranded abroad for days. The disturbance came during one of the busiest travel periods of the summer.

"This was a one in 15 million chance," NATS CEO Martin Rolfe told the BBC.

"We've processed 15 million flight plans with this system up until this point and never seen this before."

A few days ago Rolfe said that the problem would not be repeated.

On Wednesday, NATS published a report that said that the flight plan included two identically named but separate waypoint markers outside UK airspace, which forced the system to enter fail-safe mode.

"In these circumstances, the system could not reject the flight plan without a clear understanding of what possible impact it may have had. Nor could it be allowed through and risk presenting air traffic controllers with incorrect safety-critical information," NATS said.

It said that the flight plan was complying with Eurocontrol's flight planning distribution system.

UK's Civil Aviation Regulator (CAA) has said that it will review circumstances surrounding the failure.

"If there is evidence to suggest NATS may have breached its statutory and licensing obligations we will consider whether any further action is necessary," Rob Bishton, Joint-Interim Chief Executive at the UK's CAA, said in a statement.

This may mean that NATS would end up footing some of the bill for the chaos that ensued last week.

According IATA, the global airline group, the episode is likely to cost airlines up to 100 million pounds ($126 million) as travellers whose flights were cancelled would claim back expenses for the hotels or the tickets.

Britain-based airline easyJet said the NATS report left some questions unanswered. It added that though it welcomed the review, it believed a more wide-ranging examination of resources and IT systems was necessary.

"A full independent and wide-ranging review of NATS is needed to ensure it is fit for purpose today and in the future," easyJet said.

(With input from agencies)

WATCH WION LIVE HERE