Swiss authorities are insisting that vintage aircraft operator JU-Air ensures its personnel are psychologically ready before resuming services, days after a fatal Junkers Ju 52 accident.

The federal civil aviation office says that JU-Air intends to restart flights on 17 August, some two weeks after the 4 August crash in the Alps.

None of the 20 occupants of the aircraft survived the impact, which destroyed the 1939-built aircraft. Investigators have yet to understand the cause of the accident.

But JU-Air, which had suspended flights in the wake of the crash, is planning to resume services.

“As long as there is no solid suspicion of technical defects, [we] cannot order the grounding of the JU-Air fleet,” says the civil aviation office.

But it stresses that the crews and maintenance personnel must be “mentally fit”, in order to ensure the safety of operations.

It says it will temporarily ban the carrier from conducting flights if new findings emerge before 17 August that necessitate such action.