ALL 20 people on board a vintage plane were killed when the aircraft crashed into a mountainside in south-east Switzerland.

The Junkers Ju-52 plane went down on Saturday on the Piz Segnas mountain above the Swiss Alpine resort of Flims, striking the mountain’s western flank about 2540 metres (8330 feet) above sea level. The area is traditionally popular among hikers and skiers.

Police said they have now determined that all 20 people on board the plane, including its three crew members, died.

Eleven men and nine women were killed. Most of the victims were Swiss but they also included a couple and their son from Austria. The victims were aged between 42 and 84.

The plane was operated by Ju-Air, a Swiss company that offers tours with vintage former Swiss military aircraft.

Swiss officials said they are not aware of any distress call from the plane. They also expect the investigation into the cause of the crash to be “relatively complex”.

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 the crash.

Knecht explained that the vintage plane presumably did not have the crash-resistant cockpit voice and data recorders that more modern aircraft have.

He added that officials have essentially ruled out a collision with another aircraft or hitting an obstacle such as a wire.

He also said there is no indication of foul play or that the aircraft lost parts or broke up before the crash.

The plane was flying the passengers back from a two-day trip to Locarno in southern Switzerland to its base at Duebendorf, near Zurich.

Nearly 5000 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.

The company, which operates two other Ju-52s, suspended flights until further notice after the crash.