Prads-Haute-Bléone (France) - Co-pilot Andreas Lubitz (†27) was quickly presented as the cause of the crash of the Germanwings plane ten years ago , who was turned into a mentally ill mass murderer just 49 hours after the disaster. Wrongly?

Flight safety expert Simon Hradecky had learned anonymously of a defect in the cockpit door, which was therefore recorded in the aircraft's defect records. He reports this in the new Sky documentary "Germanwings - What happened on board flight 9525".

The caller later said that the entry had disappeared again. He had taken a photo as evidence, but did not want to pass it on as he feared for his job and even his life.

The fact that a press conference was held just 49 hours after the crash, in which the French public prosecutor published the most plausible and probable interpretation of an extended suicide by Lubitz, whose name he even spelled out, hit like a bomb.

Aviation journalist Andreas Spaeth knows that it usually takes weeks, if not months, to investigate airplane disasters.

The authorities are convinced that pilot Patrick Sondenheimer (†34) left the cockpit on the flight to Düsseldorf. A short time later, a buzzing sound of the door opening can be heard on the voice recorder, but this is not followed by any reaction from the co-pilot, who would have to unlock the door from the inside. Knocking noises, which turn into intense hammering, can be heard, as can the words: "Andreas, open the damn door." This is confirmed by surviving relatives in the documentary who were shown this.

According to some aviation experts, the multiple changes in altitude on the outbound flight - also in Sondenheimer's absence - also fit the scenario of the mass murderer Andreas Lubitz. The long medical list of the co-pilot, who is said to have complained of insomnia two weeks before the catastrophe, and his fear of losing his job due to an alleged visual impairment, would have prompted him to take this step.

However, according to Lufthansa CEO Carsten Spohr, Lubitz was "100 percent fit to fly without any restrictions or conditions".

According to Hradecky, unconsciousness on the part of Andreas Lubitz is still considered a possibility.

And: expert Tim van Beveren had received an indication that a crew on this aircraft had already locked themselves out once and was unable to open the door even after entering the emergency code. Specifically, button 2 - part of the emergency code - was said to have been defective.

Simon Hradecky concludes: "If the person in the cockpit was unable to act and nobody could get into the cockpit due to the defective keypad, only a technical defect could have triggered the final descent."

Book author Patrick Huber has a different opinion. According to him, "questionable theories and completely implausible conclusions" are being spread, as he writes in a comment on austrianwings.info . The statements are "nothing more than conspiracy theories". He had spoken to pilots, technicians and lawyers: "They all shook their heads."

Even ten years after the disaster that claimed 150 lives, many questions remain unanswered - perhaps forever.

The three-part documentary "Germanwings - What happened on board flight 9525?" can be seenexclusively on Sky and on the streaming service WOWfrom March 14.