Swiss officials say they're not aware of any distress call from an old-time propeller plane before it crashed in the Swiss Alps, killing 20 people.
They also expect the investigation into the cause of the crash to be “relatively complex.”
The Junkers Ju-52 plane, operated by the Swiss company Ju-Air, went down Saturday on the Piz Segnas mountain above the Alpine resort of Flims, striking the mountain's western flank about 8,330 feet above sea level. The mountainous area in southeastern Switzerland is popular with hikers and skiers and includes a glacier.
Eleven men and nine women between the ages of 42 and 84 were killed. Most of the victims were Swiss but they also included a couple and their son from Austria.
Daniel Knecht of the Swiss Transportation Safety Investigation Board said the plane appears to have hit the ground near-vertically and at high speed in Saturday's crash.
Speaking at a news conference Sunday in Flims, near the crash site, Knecht said the vintage plane presumably didn't have the crash-resistant cockpit voice and data recorders that more modern aircraft have.
He said officials have essentially ruled out a collision with another aircraft or hitting an obstacle such as a wire. He also said there's no indication of foul play or that the aircraft lost parts or broke up before the crash.
Photos released by Graubuenden canton (state) police showed the crumpled wreckage of the plane lying on the mountain, with only the upside-down tail more or less intact.
The plane was flying the passengers back from a two-day trip to Locarno in southern Switzerland to its base at Duebendorf, near Zurich. Authorities were informed of the crash at 5 p.m. Saturday, 50 minutes after the aircraft had taken off from Locarno's Magadino airfield.
Nearly 5,000 Ju-52 planes, a product of Germany's Junkers, were manufactured between 1932 and 1952.
Ju-Air's Ju-52 planes are former Swiss military aircraft, built in 1939, that were retired by the air force in 1981.
Ju-Air started operating flights with the craft in 1983; the plane that crashed — with the registration HB-HOT — had been in service with the company since 1985.
The aircraft have three engines, one on the nose and one on each wing.
The company, which operates two other Ju-52s, has suspended flights.