Lubitz’s actions during the earlier flight were masked by inputs from on-board computers that prevent a plane from flying erratically. Setting it to descend to 100 feet would have triggered a subtle, gradual drop not noticed by the captain who had left the cockpit, each time quickly curtailed by Lubitz’s subsequent instructions to return to cruise.

Contact Attempts

Today’s BEA report provides a minute-by-minute analysis of the subsequent fatal journey taken by the A320 flown by the discount arm of Deutsche Lufthansa AG, Europe’s second-largest airline, which declined to comment on the findings.

The jet’s captain left the cockpit just as it reached cruising altitude, the study says. Once alone, Lubitz changed the selected altitude from 38,000 feet to 100 feet -- a height well below the level of the mountainous terrain in the area.

During a “continuous and controlled descent” spanning 10 minutes until the impact with the ground the Marseille control center sought to contact the Germanwings plane on 11 different occasions on three frequencies, but was ignored. The French military made three attempts to get through, and the flight crew of another aircraft also radioed the jet.

The A320 captain was outside the cockpit for more than four minutes before sounding the buzzer to request readmission, the report says. When Lubitz failed to open the door he sought four times to contact him using an intercom systems.

‘Violent Blows’

Noises consistent with someone knocking on the door were also recorded on six occasions, together with muffled voices and one audible request for it to be opened, after which five “noises similar to violent blows” can be heard one.

In the cockpit, the voice recorder revealed sounds of breathing until a few seconds before impact, while the data device reveals that Lubitz maneuvered the right joystick for about 30 seconds just 1 1/2 minutes before the collision, though not sufficiently to disengage the autopilot.

Since the accident, French and German prosecutors have said Lubitz was suffering from psychological problems that weren’t fully apparent to his employer because of privacy laws designed to encourage people to consult doctors without fear.

The BEA report highlights six other crashes that appear to have been caused by an “intentional maneuver” by crew. The incidents include the crash of an Embraer SA 190 regional jet operated by LAM Mozambique Airlines in Namibia in 2013 and another involving an EgyptAir Boeing Co. 767 in 1999.

Doors Conundrum

The BEA’s final submission, expected about a year from now, will also detail lessons to be learned from the crash and suggest changes that could help prevent similar tragedies.

That may include urging regulators to review rules imposed after the Sept. 11, 2001, attacks to stop cockpit doors from being opened from the outside, though the BEA said today any changes will inevitably require a “compromise” around the conflicting risks of pilot suicide and terrorist intervention.

The airline industry’s approach to mental health seems to be the most pressing issue after Germanwings, it said.

“We must examine in detail the system of evaluating pilots, and that involves many actors, including people in the pilot’s personal life, the role of doctors, and of all the authorities,” Jouty said.

--With assistance from Richard Weiss in Frankfurt.

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