PARIS

- Passengers with moments to live screamed in terror and the pilot frantically pounded on the locked cockpit door as a German co-pilot deliberately and wordlessly smashed an Airbus carrying 150 people into an Alpine mountainside.

The account yesterday of the final moments of Germanwings Flight 9525 prompted some airlines to immediately impose stricter cockpit rules - and raised haunting questions about the motive of co-pilot Andreas Lubitz, 27, whose breathing never wavered as he destroyed the plane and the lives of those aboard.

"We have no idea of the reason," Marseille Prosecutor Brice Robin said, revealing the chilling conclusions investigators reached after reconstructing the final minutes of the flight from the plane's black box voice recorder. Co-pilot Andreas Lubitz's intention was "to destroy this plane."

French, German and U.S. officials said there was no indication of terrorism. The prosecutor did not elaborate on why investigators do not suspect a political motive; instead they're focusing on the co-pilot's "personal, family and professional environment" to try to determine why he did it.

German Chancellor Angela Merkel, whose nation lost 75 people on the flight, said the conclusions brought the tragedy to a "new, simply incomprehensible dimension." Devastated families of victims visited the crash scene yesterday, looking across a windy mountain meadow toward where their loved ones died.

Back in his hometown of Montabaur, Germany, Lubitz never appeared anything but thrilled to have landed a pilot's job with Germanwings, according to those who helped him learn to fly as a teenager.

Members of his hometown flight club in Montabaur, where he renewed his glider license last fall, said that Lubitz appeared to be happy with the job he had at the airline, a low-cost carrier in the Lufthansa Group.

After starting as a co-pilot with Germanwings in September 2013, Lubitz was upbeat when he returned to the LSC Westerwald e.V glider club to update his glider pilots' license with about 20 takeoffs.

"He was happy he had the job with Germanwings and he was doing well," said longtime club member Peter Ruecker, who watched Lubitz learn to fly. "He was very happy. He gave off a good feeling."

Club chairman Klaus Radke said he rejects the Marseille prosecutors' conclusion that Lubitz deliberately put the Germanwings flight into a descent and aimed it straight into the French Alps after the pilot had briefly left the cockpit.

"I don't see how anyone can draw such conclusions before the investigation is completed," he said.

At the house of Lubitz's parents, the curtains were drawn and four police cars were parked outside. Police blocked the media from the single-family, two-story home in a prosperous new subdivision on the edge of Montabaur, a western German town nearly 40 miles from Frankfurt.

After obtaining his glider pilot's license as a teenager, he was accepted as a Lufthansa trainee after finishing the tough German preparatory school at the town's Mons-Tabor High School.

According to Lufthansa Chief Executive Carsten Spohr, Lubitz trained in Bremen, Germany, and in Phoenix, Ariz., starting in 2008. He said there was a "several-month" gap in his training six years ago but he couldn't say what the reason was for that.

After the break, Lubitz "not only passed all medical tests but also his flight training, all flying tests and checks," Spohr told reporters, saying the co-pilot was "100 percent fit to fly, without any limitations."

After completing his training, Lubitz spent an 11-month waiting period working as a flight attendant before becoming a co-pilot on the Germanwings A320 fleet. Spohr said such a waiting period is not unusual at Lufthansa.

Lubitz had logged 630 hours' flight time by the day of the crash, the airline said.