Andreas Lubitz was a "thoroughly normal" young man - he liked having barbecues with friends, marathon running, and once had a part-time job flipping burgers.

Having spent most summer weekends as a teenager flying at his local glider club in Germany, Lubitz appeared to be on his way to fulfilling a lifelong dream when he became a co-pilot at Germanwings.

Lubitz's unremarkable background has his former colleagues and friends at a loss to explain why the 27-year-old deliberately crashed a jetliner into a mountain in the French Alps, killing himself and 149 passengers and crew.

Since the crash on Tuesday, reports have emerged of Lubitz suffering depression and having eyesight problems, while a former girlfriend recalled he had a plan to "make everyone remember" him.

Lubitz grew up in Montabaur, in western Germany. His father was a successful business executive and his mother a piano teacher.

He began flying with the LSC Westerwald glider club when he was 14, according to a profile published by major German news site, Spiegel Online.

Andi, as the club members called him, would make up to 10 flights a day, alongside other teenage flying fanatics.

"They also partied together or barbecued. They studied together for high-school final exams while waiting their turn for the next flight," Peter Rücker, the club's technician, said. "Andi was a likeable guy; we laughed together a lot."

Lubitz passed his final exams in 2007 and appeared destined for a life in the air.

An excerpt from his yearbook said Lubitz would "become a professional pilot so as to sell his cocktails around the world. … After years of training, he will participate in the Iron Man in Hawaii."

Around this time, he worked part-time as a cook at Burger King before being accepted into Lufthansa's prestigious training program, the New York Times reported.

His boss at the restaurant, Detlef Adolf, said Lubitz was punctual and reliable, and he was "overjoyed" when he was accepted into pilot training: "He was happy - happy that he passed."

One of the first reports about Lubitz's background that caused concern following the crash was that he withdrew from training for some months.

But he completed his studies, and worked as a flight attendant until a co-pilot's role came up at Lufthansa's budget airline Germanwings in 2013, clocking up more than 600 flying hours.

Lubitz went back to where it all began - the glider club - last year to do some flying to keep his glider's license current.

Club chairman Klaus Radke told The New York Times that Lubitz appeared to be fit, professional and self-assured.

"When I saw him as an adult compared to a youth, I thought, 'He really amounted to something,'" Mr Radke said.

"He was confident, helpful. I thought, 'Man, he's someone who made it.' "

Mr Radke, who said the club had received death threats since the crash, did not see anything amiss the last time he saw Lubitz.

"I'm not a doctor," Mr Radke said. "For me he was normal."

A former girlfriend, 26-year-old "Maria W" told Bild newspaper that when she heard about the crash she remembered that he had said he was going do something "that would change the system" and "make everyone remember" him.

She added: "It didn't make sense at the time but now it all does."

Maria, who is thought to have met Lubitz at work, said he would wake up at night screaming : "We're going down."

On Saturday, unnamed officials told The New York Times that Lubitz was suffering from eyesight problems that could end his career, and had psychological issues, some of which he hid from his employer.

The Spiegel Online profile, compiled by more than 20 journalists, concluded it was "disturbing" that looking into Lubitz's background revealed very little about his motives for the crash.

"A closer look at the life of a co-pilot who became a murderer shows a lot of signs of ordinariness, with nothing to indicate he might be close to the abyss.

"Throughout his life, Lubitz cracked ordinary jokes, he listened to ordinary music and he wrote ordinary things. By all appearances, he seemed to be just a normal guy."

Fairfax Media