PARIS — Andreas Lubitz, the co-pilot suspected of deliberately flying a German airliner into the French Alps, appears to have rehearsed the plane’s fatal dive during an earlier flight on the day of the crash, the French authorities said in a preliminary report published on Wednesday.
The initial findings by the Bureau of Investigations and Analyses, known by its French abbreviation B.E.A., show that the co-pilot repeatedly set the Germanwings plane’s altitude to 100 feet during its outbound flight to Barcelona, Spain, from Düsseldorf, Germany, on March 24.
The maneuvers, which were captured by the plane’s flight data recorder, took place while the flight’s captain had left the cockpit temporarily.
“To us, it is clear that this was some kind of rehearsal,” Rémi Jouty, the director of the B.E.A., said in a telephone interview. “We see the same actions being taken in the same circumstances, at a moment when the co-pilot was alone in the cockpit.”
The new information contained in the 29-page report provides further evidence suggesting that the 27-year-old co-pilot crashed the Airbus A320 intentionally after locking the captain out of the cockpit, killing himself and 149 others, on its return leg to Düsseldorf.
An initial analysis of a cockpit audio recording retrieved from one of the plane’s so-called black boxes just days after the crash led a French prosecutor to declare that Mr. Lubitz had acted deliberately.
Investigations by the German police later revealed that Mr. Lubitz had a history of severe depression dating to at least 2009, and that he had scoured the Internet for methods of committing suicide in the days before his final flight.
The French report indicates that Mr. Lubitz’s trial run was so fleeting that it went undetected by air traffic controllers, who had already given instructions for a moderate descent to 35,000 feet from 37,000 feet. The flight’s captain, Patrick Sondenheimer, also apparently did not notice the maneuvers, which occurred about 20 minutes into the flight and while the captain was out of the cockpit for roughly five minutes.
The report says that the co-pilot selected a target altitude of 100 feet “several times” for durations ranging from a few seconds to up to three minutes during the captain’s absence.
French investigators did not try to explain Mr. Lubitz’s actions, but they were unambiguous about his role in the crash.
“We cannot presume what was going on in his mind,” Mr. Jouty said. “But based on all the information that we have gathered so far, we can affirm, categorically, that this crash was the result of an intentional act,” he continued, “a series of steps that, taken together, all point in the same direction.”
The report notes similarities between his control inputs on the two flights and, in its analysis of the second, ill-fated flight, supports the French prosecutor’s initial conclusions. The co-pilot “intentionally modified the autopilot instructions to order the airplane to descend until it collided with the terrain,” according to the report.
“He did not open the cockpit door during the descent, despite requests for access made via the keypad, the cabin interphone and knocks on the door,” it said.
In the wake of the crash, Germany established a task force of aviation, medical and government experts to study the circumstances that led to the fatal descent and how it might have been averted.
Last month, two working groups met to discuss possible changes to cockpit door security systems and to review the standards for monitoring pilots’ mental health. The group expects to publish its initial findings before the summer.
The European Commission in Brussels is also expected in the coming days to announce the formation of a high-level working group that would also be tasked with proposing new rules intended to prevent similar disasters. Although Mr. Lubitz is the highest-profile example of pilot suicide, his was not an isolated case. Over the past two decades, a series of fatal airline crashes have been attributed to deliberate actions by the pilot.
The B.E.A. investigation is limited solely to determining the facts of the case and to making recommendations to safety regulators with the intent to reduce the risk of a similar episode. Unlike the separate criminal inquiry being conducted by French prosecutors, it will not seek to apportion legal responsibility for the crash.
France is one of a handful of countries that routinely seek criminal indictments in air accidents, regardless of whether there is clear evidence of criminal intent or negligence. Such indictments typically target the airline, legal experts said, but they can include individuals as well.
Any criminal case against Germanwings and its parent company, Lufthansa, will hinge on whether prosecutors can prove that the airline was negligent in its oversight of Mr. Lubitz.
Evidence uncovered by German prosecutors after the crash indicates that Mr. Lubitz had sought treatment for psychological issues in the months before the flight, but that he had hidden his illness from his employer.
Lufthansa has admitted that Mr. Lubitz informed the company of a previous episode of severe depression, which had led him to interrupt his pilot training for several months in 2009. Mr. Lubitz was later reinstated after an evaluation by a flight doctor found him fit to return to the cockpit. But the airline does not appear to have imposed any special monitoring of him beyond the minimum required for any pilot who had a flagged health issue.
The French report says that Mr. Lubitz started his basic training at the Bremen campus of Lufthansa’s prestigious flight school in September 2008, but suspended it just two months later for “medical reasons.”
He did not resume his training until late August 2009.
During his absence, Lufthansa’s flight doctors twice refused to certify Mr. Lubitz as fit to fly, citing his depression and the medicine he had been prescribed to treat it.
According to the French report, a Lufthansa doctor informed Germany’s Federal Aviation Office, which licenses pilots, that Mr. Lubitz had been denied medical clearance on July 14, 2009.
But two weeks later, he received a valid “Class 1” medical certificate that noted that he had a medical condition, although it did not specify whether it was related to a psychological issue. The flag instructed flight doctors to contact the aviation office before evaluating Mr. Lubitz for his required annual physical.
Barbara Schädler, a Lufthansa spokeswoman, declined to comment on the French report. A spokeswoman for the German regulator did not immediately respond to telephone calls or emails requesting comment.
Because of Germany’s strict privacy laws, the details of Mr. Lubitz’s condition and of his treatment were never shared with Lufthansa managers. Flight doctors who examined him after his reinstatement reported no signs that his depression had returned — something that would have set off an alert to the airline and to German regulators.
But documents made public last week showed that Mr. Lubitz’s depression did catch the attention of American regulators. The Federal Aviation Administration raised questions about Mr. Lubitz’s fitness to fly in 2010, when he sought a student pilot’s license to continue his training at a Lufthansa-owned flight school in Arizona.
According to the documents, the United States aviation authority ultimately granted Mr. Lubitz a license after a doctor in Germany certified that he had recovered fully and was no longer taking antidepressants.
The French report indicates that Mr. Lubitz was in Arizona for four months, from November 2010 until March 2011, before returning to Germany. He continued his flight training while also working under contract as a Lufthansa flight attendant for another two years, significantly longer than the 11 months that the airline had previously disclosed, before being hired by Germanwings.
He did not become a fully licensed commercial pilot until February 2014, barely more than a year before he crashed the plane into a mountainside.
Given the worldwide attention the crash has received, French prosecutors are widely expected to move ahead with a criminal indictment, despite some diplomatic pressure to transfer the case to a German court. Brice Robin, the prosecutor in Marseille who is tasked with the investigation, is expected to reach a formal decision about whether to proceed before the summer.
“I cannot imagine that the prosecutor would close this case,” said Stéphane Gicquel, secretary general of Fenvac, a French association that represents the families of accident and disaster victims. “It is too high-profile.”