The ill-fated aircraft, Ju-Air said, was built in 1939, flew 10,187 hours and prior to the crash had undergone regular maintenance.

Switzerland police have confirmed the deaths of 20 people after a World War II vintage aircraft crashed into a mountainside in the eastern region of the country.

"Based on the situation at the crash site we can say that the aircraft smashed into ground almost vertically at relatively high speed," said Daniel Knecht of the Swiss Transportation Safety Investigation Board.

"What we can rule out at this point is that there had been a collision before the crash, neither with another aircraft nor with some other obstacle such as a cable."

The Junkers JU-52 HB-HOT aircraft, which was carrying out a routine tour, reportedly had 17 passengers and three crew aboard. An official cause of the accident yet to be reported. According to a BBC report, the airplane had no black box and little radar monitoring. 

Ju-Air said that the aircraft was built in 1939, flew 10,187 hours and prior to the crash had undergone regular maintenance.

There were 11 men and nine were women, aged from 42 to 84 years old, police spokeswoman Anita Senti said in a press conference.

JU-Air set up a helpline for relatives of the deceased and suspended all flights until further notice.