Heat wave could be behind Swiss crash of vintage plane that killed 20 in the Alps

Elizabeth Weise | USA TODAY

Show Caption Hide Caption Vintage propeller plane crashes in Swiss mountain, killing all on board The 1939 Junkers Ju 52 plane was 50 minutes into its flight when it crashed. Officials say the investigation into what happened will be "relatively complex."

A record heatwave across Europe that sent temperatures in Switzerland as high as 94 may have caused the crash of a vintage propeller plane that slammed into the side of a Swiss mountain Saturday, killing all 20 onboard.

The plane went straight down, crashing almost vertically into the western flank of the Piz Segnas mountain at 8,300 feet at about 5:00 pm local time Saturday. When it crashed it was going at a high rate of speed, officials said.

Photos released by state police in the area showed the crumpled wreckage of the plane, with only the tail, twisted over and upside down, still somewhat intact.

Police said those killed included 14 Swiss, a three-member family from Austria and three Swiss crew members.The passengers were 42 to 84 years old, authorities said.

The 1939 Junkers Ju 52, of a type nicknamed Iron Annie, was returning from the resort town of Locarno in southern Switzerland.

The plane was about 50 minutes into its flight when it crashed. Authorities said no emergency call was made in the moments before the plunge.

"High temperatures can affect the performance of an aircraft," Daniel Knecht from the Swiss safety investigation agency said in a press conference held Sunday near the crash site in the Alpine resort of Flims, Switzerland.

While heat itself doesn’t harm the plane, it can affect how it flies, as heat is associated with a thinning of the air. "The aircraft has less power at the same altitude, you can feel it at the start or in a curve," Knecht said in the news conference, as reported by the Swiss German-language newspaper the Neue Zürcher Zeitung.

A family of four was killed when their small plane went down in a forested mountain pass Saturday morning west of Lucerne, Switzerland. That crash is also under investigation.

Kurt Waldmeier, co-founder of Ju-Air, the company that operated the flights, said the pilot was very experienced. The 62-year-old had flown more than 30 years for the airlines Swiss and Swissair and the Swiss Air Force. The copilot, 63, had flown more than 30 years as a line and military pilot, Waldmeier said at the news conference.

Europe has been sweltering under a record heatwave that sent temperatures in Lisbon, Portugal to 102, hotter than California’s Death Valley, which was at 99.

In Switzerland it was so hot that the army allowed soldiers to wear shorts and T-shirts instead of uniforms and police in Zurich urged dog owners to equip their dogs with shoes to protect their paws from dangerously hot sidewalks.

The Swiss-based JU-Air service offers sightseeing and adventure flights in three mid-century Junkers Ju-52 aircraft, which were decommissioned by the Swiss Air Force.

Although the plane was 79 years old, Waldmeier said age was not a factor. It had been well-maintained and like the other two Ju 52s the company operates, and was serviced every 35 hours. It had only flown five hours since its last maintenance, he said.

Because of its antique nature, the airplane had no black box so authorities will not be able to use that to determine what happened.

Swiss aviation authorities have ruled out outside interference, collision with a cable or other obstacles. There was also no evidence that the aircraft has lost any parts or been broken up in the air, Knecht said at the news conference.

Nearly 5,000 of the Ju-52 planes were manufactured between 1932 and 1952. Fewer than ten are still flying. The aircraft have three engines, one on the nose and one on each wing.

Swiss Ju-Air began operating flights with the vintage planes in 1983. It has suspended all flights until further notice, according to its website.