French rescue workers in Le Vernet hold the flags of Germany and Japan during a remembrance ceremony Sunday near the crash site. (Jean-Paul Pelissier/Reuters)

The co-pilot who crashed Germanwings Flight 9525 had consulted with several medical professionals about a vision issue that, coupled with preexisting psychological problems, appeared to give him a growing sense of unease about his ability to keep his job, according to officials familiar with the investigation.

German police, one official said Sunday, had discovered documents in Andreas Lubitz’s apartment in his handwriting in which he had written short phrases conveying deep stress about vision issues. He appeared to believe that those problems were serious enough to challenge his ability to continue working as an airline pilot — a job that had been the longtime ambition of the reserved 27-year-old.

Although there is no sign that Lubitz kept a diary, the papers made clear that he was concerned about his future. He had consulted several medical professionals about the issue, the official said, and investigators are examining the medical records they have collected from doctors.

A second official familiar with the investigation said German authorities, in their searches of Lubitz’s homes and belongings, also found prescription medications that showed he was being treated for psychological problems. Both officials agreed to talk on the condition of anonymity because the investigation is ongoing.

But investigators have discovered few obvious signs that Lubitz had pre-planned a suicide or a deliberate crashing of a plane, and one working theory is that he altered Flight 9525’s course on a deadly whim. When the flight’s more experienced pilot left the cockpit to go to the bathroom, Lubitz may have seized the opportunity to crash the plane, the first official said.

Germany’s Bild newspaper reported that airline co-pilot Andreas Lubitz, suspected of deliberately crashing a plane in the French Alps, told a former girlfriend that he was planning a big gesture. (Reuters)

Investigators are examining Lubitz’s voluminous electronic trail, contained on an iPad, an iPhone and a computer. But nothing discovered thus far in his electronic history foreshadows the fatal incident, the official said.

French investigators are working alongside their German counterparts in Düsseldorf, the official said. U.S. officials are also assisting from afar, because Americans died in the crash. The U.S. investigators have helped in tracking down Lubitz’s trail on Facebook, because they have better access to the U.S.-based social network than their European counterparts do.

On Sunday, Germany’s Bild newspaper disclosed new details about the “black box” recordings of the Airbus A320, which was en route from Barcelona to Düsseldorf and crashed Tuesday in the French Alps.

Early on, the flight’s captain is heard apologizing to passengers for a delayed takeoff. About 20 minutes later, the pilot is heard talking to Lubitz and mentioning that he did not make it to the bathroom in Barcelona before the flight. Lubitz — who, investigators say, initiated the fatal descent after the pilot left the cockpit — is heard saying that he is willing to take over at any time.

At one point, according to Bild, the pilot asks Lubitz to plan for the flight’s landing in Düsseldorf. Lubitz is heard responding oddly, using conditional phrasing about the landing, such as “hopefully” and “we’ll see.”

The pilot is heard exiting the cockpit and later attempts to get back in but is locked out. As the pilot grows more desperate to reenter the cockpit, a loud bang is heard; he appears to be trying to break down the door. He is heard shouting, “For God’s sake, open the door.”

Although French prosecutors have said that passengers’ screams were heard shortly before the crash, the Bild report suggests that the pilot’s frantic attempts to get back into the cockpit caused audible panic several minutes before the crash.

Marseille prosecutor Brice Robin said Sunday that DNA traces of 78 victims had been found at the mountainside crash site, where investigators have been struggling with the logistics of the forbidding landscape. He said a road would be constructed by Monday that would ease the transport of debris for further examination. Investigators have not found key parts of the flight data recorder that would help them determine technical information about the plane’s final descent.

Family members of the victims, meanwhile, were processing the loss of their loved ones. Very few have spoken publicly, but Philip Bramley, a British man whose son, Paul Bramley, was among the dead, read a statement to TV cameras Saturday calling the co-pilot’s motive for crashing the plane “not relevant.”

“What happened on the morning of 24 March was the act of a person who at the very least was ill,” he said. “If there was a motive or reason, we don’t want to hear it. It’s not relevant. What is relevant is this should never happen again. My son and everyone on that plane should not be forgotten ever.”

One factor that remains a question mark in the case is how or whether Lubitz’s relationship with his girlfriend played a role in his state of mind at the time of the crash. The two had appeared to be living together at Lubitz’s apartment in Düsseldorf.

The woman, whom the German news outlet Der Spiegel described as a math teacher, has been interviewed by authorities.

Faiola reported from Montabaur, Germany. Stephanie Kirchner in Montabaur contributed to this report.

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Flight 9525’s final moments, minute by minute