The Swiss airline had voluntarily suspended its flight operations after the World War II vintage plane crashed into the Piz Segnas mountain, in the eastern canton of Grisons, at an altitude of 2,500 metres.
The Swiss Transport Safety Investigation Board is still investigating the cause of the crash, a task rendered harder by the fact that the vintage plan did not have a black box.
“The plane turned 180 degrees to the south and fell to the ground like a stone,” a witness told Swiss news portal 20 Minutes, adding that the debris was scattered over “a very small area,” indicating an explosion was unlikely the cause of the crash. All seventeen passengers and the flight's three crew members were killed.
“As long as no firm suspicion of a technical defect exists, BAZL can not order a grounding of the JU-Air fleet,” a spokesperson for Switzerland's Federal Office of Civil Aviation (BAZL) was reported as saying by news outlet SRF.
“The plane crashed almost vertically and hit the ground at a relatively high speed,” Daniel Knecht from the Swiss Transport Safety Investigation Board told Media two days after the crash. He added that investigators had ruled out the possibility that the plane had collided with another object, such as a cable or another plane.
The JU-52 HB-HOT aircraft which crashed in the Alps on August 4th was built in 1939 and had completed 10,187 flight hours. It had to be serviced every 35 flight hours and underwent its last technical check up in late July, only a few days before the fatal crash en route from Locarno to Ju-Air's base in Dübendorf.
Both pilots were experienced and had flown for Swissair and the military for more than 30 years, according to a JU-Air statement.
JU-Air will resume flights with its remaining vintage planes “unless new questions or question marks emerge that question safety. If we are not sure that we can operate these aircraft safely then they certainly will not start,” said Christian Gartmann, a JU-Air spokesman, according to SRF.
The Civil Aviation Authority said it can only implement a flight ban on the company if a technical fault is found to be the reason behind the crash or if JU-Air's staff are not in a mentally fit condition to resume operations.
JU-Air's Gartmann argued that the two weeks compassionate leave given to the company's employees “was enough time to take a break and to deal with this situation.”
Debris from site of the crash has now been cleared away and the bodies have been recovered. The Swiss Transport Safety Investigation Board continues to investigate the cause of the accident and the office of the attorney general could still file criminal charges, depending on the outcome of the investigation.
JU-Air operates private and charter flights out of Dübendorf, in the canton of Zurich, to Locarno, Bern and Engadin, among other routes.
Austrian aviation news portal Austrian Wings suggested the crash may have been caused by the plane's engines failing to generate enough power following the 180-degree curve undertaken by the pilots because of turbulence and forecast thunderstorms. The unusually hot temperatures combined with the altitude might have affected the stall speed – “the critical speed at which the air flow on the wings tears off and a machine is no longer able to fly” – writes the portal.
The same source suggested that photos, if recoverable, taken by passengers or crew on their smartphones may ultimately be able to provide the answers.