(Bloomberg) -- The Germanwings pilot who investigators saycrashed his plane into a French mountain in March repeatedly setthe jet on collision course with the ground on a flight earlierthat day in what may have been a dry run for his suicide bid.

Data from the morning flight shows Andreas Lubitz briefly setthe Airbus Group NV A320 jet to descend to 100 feet on fiveoccasions when his captain left the cockpit before returning it tocruise mode, France’s air-accident investigator said May 6.

“I can’t know what was in the pilot’s head,” BEA Director RemiJouty said as he presented a preliminary report on the March 24crash. “All we can do is say that, several times, he manipulatedthe button to put in a minimum value.”

The maneuvers on the flight from Dusseldorf to Barcelona wererepeated hours later on the return journey when Lubitz sent theairliner into a fatal plunge after denying his senior colleagueaccess to the flight deck following a toilet break. The impact withan Alpine slope shattered the jet into thousands of pieces, killingall 150 people on board.

Lubitz’s actions during the earlier flight were masked by inputsfrom on-board computers that prevent a plane from flyingerratically. Setting it to descend to 100 feet would have triggereda subtle, gradual drop not noticed by the captain who had left thecockpit, each time quickly curtailed by Lubitz’s subsequentinstructions to return to cruise.

Contact Attempts

Today’s BEA report provides a minute-by-minute analysis of thesubsequent fatal journey taken by the A320 flown by the discountarm 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 cruisingaltitude, the study says. Once alone, Lubitz changed the selectedaltitude from 38,000 feet to 100 feet -- a height well below thelevel of the mountainous terrain in the area.

During a “continuous and controlled descent” spanning 10 minutesuntil the impact with the ground the Marseille control centersought to contact the Germanwings plane on 11 different occasionson three frequencies, but was ignored. The French military madethree attempts to get through, and the flight crew of anotheraircraft also radioed the jet.

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

‘Violent Blows’

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

In the cockpit, the voice recorder revealed sounds of breathinguntil a few seconds before impact, while the data device revealsthat Lubitz maneuvered the right joystick for about 30 seconds just1 1/2 minutes before the collision, though not sufficiently todisengage the autopilot.

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

The BEA report highlights six other crashes that appear to havebeen caused by an “intentional maneuver” by crew. The incidentsinclude the crash of an Embraer SA 190 regional jet operated by LAMMozambique Airlines in Namibia in 2013 and another involving anEgyptAir Boeing Co. 767 in 1999.

Doors Conundrum

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

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

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

“We must examine in detail the system of evaluating pilots, andthat involves many actors, including people in the pilot’s personallife, the role of doctors, and of all the authorities,” Joutysaid.

--With assistance from Richard Weiss in Frankfurt.

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