A Ryanair aircraft “marginally avoided” crashing after the airline failed to inform its pilots of changes to the approach to an airport, according to the official report on the incident.

The aircraft emerged from low cloud only 400ft from the ground, triggering an alarm and forcing the captain to make an emergency ascent.

The Irish airline also failed to report the incident to Ireland’s Air Accident Investigation Unit for almost two weeks, by which time some of the evidence had been deleted.

The Boeing 737, carrying 144 passengers and crew, was flying from Gatwick to Knock, in the west of Ireland, on March 23.

Several navigational aids, which help pilots land in poor visibility, had been switched off at Knock while the airport was upgraded. Ryanair had been informed of the changes six weeks earlier but, despite being one of the main operators at Knock, it did not pass on the information to its pilots.

This led the pilots to programme the wrong approach information into the aircraft’s flight computer, which manages the autopilot. An air traffic controller told the pilots, as they approached Knock, that they had to alter their approach. They became “so engrossed” by the need to update the computer that they did not realise they were descending at a fast rate and becoming dangerously close to the ground.

The report said: “The work overload meant normal routine checks were not carried out and there was no questioning of the developing situation by either pilot. When they finally broke clear of cloud at about 400ft, the spatial reality finally dawned on both pilots as the pilot flying disengaged the autopilot and executed a non-procedural go-around.”

The investigators found the pilots failed to respond quickly enough to the changing circumstances and the captain allowed himself to become distracted from the task of flying the plane. But the report concluded that the root of the problem lay in the failure to give the pilots the correct information to plot a safe course.

A cockpit manual, supplied by an outside company, had also not been updated with the new information about Knock.

Both pilots had long experience of flying older 737s but had only recently switched to the modern, highly automated version of the aircraft operated by Ryanair.

“This cognitive deficit led to their difficulties in managing and interacting with the Boeing 737-800 automations,” the report said. It concluded: “This serious incident is defined as controlled flight into terrain only marginally avoided.”

The investigators also criticised the “unacceptable delay” by Ryanair in notifying them of the incident. Information about the flight had been recorded on devices in the cockpit but these had been overwritten during subsequent flights.

David Learmount, safety editor of Flight International magazine, said Ryanair had reduced costs by operating a computer-based briefing system for pilots, who check it for updates 45 minutes before their flights.

He said: “If they are going to rely on this system it is very important that they keep it up to date. The absence of the information created extra pressure on the pilots which distracted them. They got an awful shock coming out of the cloud base to find how close the ground was.”

Ryanair has accepted a series of safety recommendations made by the investigators to prevent a repeat of the incident.

The airline refused to answer questions during a phone call yesterday and insisted they be put in writing. It then failed to respond to emails.

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