The actions of the Germanwings pilot embroiled in an investigation into Tuesday’s crash has left Lufthansa’s ceo speechless at news he appears to have intentionally downed the plane.

The reportedly 27 or 28 year old co-pilot in the centre of the investigation was said to have been “100% flightworthy without any limitations,” according to Lufthansa’s ceo, despite having verified the pilot took a break during his training with speculation mounting it may have been for medical reasons.

Reported by The New York Times, chief French prosecutor handling the criminal investigation, Brice Robin, said co-pilot of flight U49525, Andreas Lubitz, had deliberately set out to “destroy the aircraft”, after locking out the second pilot from the cockpit ignoring frantic knocks and putting the flight on its fatal descent following the retrieval of voice recorder evidence.

Following the report, officials at Germanwings and parent company Lufthansa said if Lubitz committed the act, his motivation remained a mystery to them.

“We have no indication what could have led the co-pilot to commit this terrible act,” Lufthansa ceo, Carsten Spohr said at a news conference after the French prosecutor described the last minutes of the flight.

“Such an isolated act can never be completely ruled out. The best system in the world can’t stop it.”

“It leaves us absolutely speechless. I would not have been able to imagine that the situation would have got even worse,” Spohr said.

According to the NYTimes, the prosecutor said the voice recorder transcript revealed the captain was preparing a briefing for landing in Düsseldorf and the co-pilot’s answer was “laconic.”

“The commanding pilot then asks the co-pilot to take over, and the noise of a seat backing up and a door closing can be heard,” the paper reports.

“At this stage, the co-pilot is in control, alone,” the prosecutor said. “It is when he is alone that the co-pilot manipulates the flight monitoring system to activate the descent of the plane.” The prosecutor said that this action could only have been “voluntary.”

According to Robin, the control the co-pilot activated required several turns, and the flight could not have been turned to such a low altitude accidentally.

“You can hear the commanding pilot ask for access to the cockpit several times,” the prosecutor said. “He identifies himself, but the co-pilot does not provide any answer.”

“You can hear human breathing in the cockpit up until the moment of impact,” Robin said, adding the breathing did not indicate any health problems such as a heart attack.

Passengers could be heard screaming before the crash, Robin said and that during the descent air traffic controllers repeatedly attempted to contact the plane but received no response.

Upon questioning whether the co-pilot had committed suicide, he replied, “I am not a legal expert.” He added, “But when one person is responsible for 150 lives, it is more than suicide.”

Lubitz began pilot training in 2008 and had racked up 630 hours of flying experience at the time of the fatal crash on Tuesday.

Lufthansa officials confirmed that while the flight-school programme usually lasts between 18 months to 24 months, Lubitz interrupted his training six years ago for an unknown reason.

However, if it was due to medical reasons, Spohr said it would be unknown because of Germany’s privacy rules regarding medical records.

Lubitz eventually completed training and passed all medical “with flying colours”, as well as necessary flying tests, Spohr said, joining Germanwings as a pilot in 2013.

“He was 100 percent flightworthy without any limitations,” Spohr told reporters.

Spohr said there was no indication the crash was linked to an act of terrorism and prosecutors have found no links between any of the passengers or crew on board to terrorism.

While Lufthansa does not voluntarily implement protocols that require at least two pilots in the cockpit at any given time, other airlines around the world are implementing new policies today in the aftermath of the crash.

Image: Lufthansa CEO Carsten Spohr (Reuters/Kai Pfaffenbach)