Swiss air crash investigators are inspecting the wreck of a vintage plane that plunged vertically from the sky on Saturday at high speed, killing all 20 people on board.

The crash took place in the canton of Graubünden in a basin near the Piz Segnas mountain, some 2,400 metres above sea level.

The JU-52 plane was carrying 11 men and nine women, aged between 42 and 84 years, mostly from Switzerland and one couple and their son from Austria.

All relatives have been informed and the recovery of the bodies is likely to take some time, police said.

“Rescue services encountered a sad sight at the scene,” said Mr Andreas Tobler, local police chief, at a press conference showing images of the mangled wreckage.

There are several eye-witnesses to the crash who said the plane dropped vertically from the sky.



A view of the accident site near the mountain resort of Flims, Switzerland. Photograph: REUTERS/Arnd Wiegmann Police declined to share any more details from eye-witnesses and said there was no black box.

“We will see what we need for the investigation but, as far as I know, there are no technical recordings available,” said Mr Tobler.

With some 100 investigators at the scene, technical experts said on Sunday afternoon they were still unsure what caused the JU-52 plane to drop from the sky, but said it was likely a combination of factors were at play, including the extreme temperatures of over 30 degrees.

“Hot air is thinner and if you have thin air it limits the capacity of the motors so you have less efficiency,” said Mr Daniel Knecht of the Swiss air crash investigators (SUST). “But it is possible to deal with that so heat or wind alone are not a danger.”

He said there was no reason to think the vintage plane, a so-called “Juncker” mid-century model, was unsafe.

“There is no clear link between age and safety,” he said. “Even an older aircraft, correctly maintained, can be flown safely.”

The plane seated 17 passengers along with two pilots and a flight attendant.

Fully booked for its last flight, it was owned by airline JU-Air and was flying from Locarno in the south of Switzerland to the airline’s base in Dübendorf, Zürich.

Undated photo of a JU-52 aircraft, flown by JU-Air, mid-flight. File photograph: Ju-Air/Keystone/AP “Yesterday was the most difficult and dark day in the 36-year history of JU-Air,” said airline chief Kurt Waldmeier. “The pilots were very experienced.”

The firm has a clean security record offering sightseeing, charter and adventure flights with three mid-century Junkers Ju-52 aircraft, decommissioned by the Swiss Air Force.