London airspace closure was 'simply unacceptable': Nats faces political onslaught as delays and cancellations continue

Chair of Transport Select Committee vows to 'get to the bottom' of what happened on Friday afternoon

Disruption continued through today for British Airways' short-haul operation at Heathrow, with 33 more cancellations (PA)

As nearly 1,000 people caught in the aftermath of Friday’s air-traffic control chaos remained out of position, Nats faced angry questions from politicians about the "unprecedented" computer failure at the Swanwick Centre.

Louise Ellman, Chair of the Transport Select Committee, deplored "the impact of the disruption this failure has caused on airports, airlines and passengers" and vowed to "get to the bottom of what led up to this weekend’s events”.

The Transport Secretary, Patrick McLoughlin, has already described the shutdown of much of southern England’s airspace as "simply unacceptable". He is due to appear before the committee on Monday to answer unrelated questions on rail investment. Ms Ellman indicated she would take the opportunity to ask him about the air-traffic control failure to establish "what Nats must do in order to ensure the same problem does not recur in future."

Nearly 24 hours after the failure, a Nats statement pinned the blame on a hitherto unknown fault that appeared when work stations were being switched between standby and active modes: "Transition between the two states caused a failure in the system which has not been seen before. The failure meant that the controllers were unable to access all of the data regarding individual flight plans which significantly increases their workload."

The number of aircraft that could safely be handled was drastically reduced, leading to more than 100 flight cancellations at Heathrow, Gatwick and London City.

Politicians and passengers will want to find out if staff cuts at Nats exacerbated the problem. In June, the firm’s chief executive, Richard Deakin, told the Transport Select Committee: "We have been on a steady journey to reduce costs. That of course takes into account our direct operating costs and people, so we are going through a redundancy programme this year."

Disruption continued through today for British Airways' short-haul operation at Heathrow, with 33 more cancellations.

The worst-affected passengers were those booked on BA’s Friday night Airbus A380 flight to Johannesburg. The airline cancelled a swathe of European flights to protect its entire long-haul programme, and nearly 500 passengers and crew were expecting flight BA55 to take off. But the delay as the backlog was cleared rendered the crew "out of hours" – unable to complete the flight within the remaining duty time. It was grounded for over 22 hours, finally pushing back at 4.23pm this afternoon. A similar number of people were waiting in South Africa for the jet, and will now fly home during the day on Sunday rather than overnight tonight.

Passengers are not entitled to financial compensation for delays, because the failure counts as an "extraordinary circumstance". But airlines have an open-ended obligation to pay for passengers’ hotels and meal until they are able to fly. The single round-trip to Johannesburg alone is likely to cost BA more than £50,000. The financial impact across all airlines will run to several million.

However, the cost of Friday’s failure remains tiny compared with the impact of air-traffic control strikes on the Continent this year. Industrial action in Italy on Friday alone had far more effect, with easyJet cancelling 70 flights - compared with 10 in the UK - and Ryanair cancelling nearly 200 departures.