On 4 August 2018, a Junkers Ju 52 passenger aircraft operated by Ju-Air crashed near Piz Segnas, Switzerland, while en route from Locarno to Dübendorf.

The report also found that the aircraft was not airworthy at the time of flight, in that the engines were not producing their minimum rated power and that the company had a deficient safety culture of rule breaking.

It had served with the Swiss Air Force from 1939 to 1985, when it was acquired by the Association of the Friends of the Swiss Air Force (German: Verein der Freunde der Schweizerischen Luftwaffe), which operated under the name Ju-Air, a company that offers sightseeing flights on vintage aircraft, and had logged 10,000 hours of flight time.

[5] The aircraft had been issued with a certificate of airworthiness by the Federal Office of Civil Aviation (FOCA) on 6 April 2018, valid for two years.

After reaching Lake Maggiore and commencing an 180 degree turn, the aircraft flew above the Blenio Valley and steadily gained altitude.

[3]: 11–19 The flight eventually flew past the Tschingelhörner peaks and continued to fly towards the Martinsloch, a rock window gaping at the ridges nearby.

[3]: 11–19 At 16:56 local time (14:56 UTC),[6] the Junkers crashed into Piz Segnas mountain, at an elevation of 2,540 metres (8,330 ft) and a speed of 200 km/h at an almost vertical angle.

[5] A spokesperson for the STSB said that the Junkers "fell like a stone to the ground",[17] and that the heatwave in Europe could have been a factor in the crash, as heat reduces an aircraft's climb performance.

[8] Investigators hoped to find some relevant information from passengers' personal photographic and video recordings during the sightseeing flight.

Environmental factors played a big role in the crash as the crew's intention to take the scenic route, which involved flying near the Piz Segnas, caused changes on the external condition that threatened the safety of the flight.

The decision to fly through the risky route, however, was already shaped by the lack of safety cultures and routine violations by the crew and the company itself.

The clear sky condition and high elevation of the area also altered the aircraft's performance due to the lowered air density.

Deeper investigation uncovered several findings about the conduct of the pilots on previous flights, which showed that they had flown recklessly multiple times.

Pilot A was noted to have been repeatedly violating the safety altitude by flying the aircraft lower than it was supposed to be, which was dismissed by his instructor who later graded him as "standard".

[3]: 58–59 The existing regulation from EASA outlined that the Ju-Air Junkers Ju 52 were obliged to fly with a minimum distance of 2,000 feet above any terrain within 9.3 km of the route.

[3]: 43–44 Following the discovery of pilots flying aircraft in high-risk, investigators managed to identify the factors that caused such disregard to safety.

The other factor was the lack of rules regarding the operation of vintage aircraft and overlook from the local aviation authority regarding the compliance with the existing regulations.

Inspection on the maintenance shed light on the poor servicing of the aircraft as the involved one was found with extensive corrosion and cracks.

FOCA deemed them unsafe to fly due to the maintenance issues found in the HB-HOT wreck, such as fatigue cracks, corrosion and sub-standard repair work.

Several deficiencies were actively dismissed by inspectors from FOCA, including the miscalculation of the basic empty mass which contributed to the shift in the aircraft's center of gravity.

The internal safety management of the airline was also deemed inadequate as it didn't issue any corrective measures regarding high-risk flights that had been happening for years.

The STSB found that the aircraft was not in an airworthy condition when it took off on the accident flight, in that the engines had not been properly maintained and were not producing rated power.