In a stunning turn of events, French prosecutors investigating Tuesday's crash of a Germanwings Airbus have said they believe that the plane's co-pilot caused the crash deliberately. The co-pilot, 28-year-old Andreas Lubitz, apparently refused to readmit the flight's captain back into the cockpit. He then took full control of the plane, directing it into the French Alps, where it disintegrated on impact, killing all 150 people onboard.

The lead investigator, Brice Robin, announced at a press conference in Marseille, France, on Thursday that his team had listened to the cockpit's voice recorder (the "black box") to make their shocking determination. "At this moment, in light of investigation, the interpretation we can give at this time is that the co-pilot through voluntary abstention refused to open the door of the cockpit to the commander, and activated the button that commands the loss of altitude," Robin said.

Lubitz's reasons for doing so remain unknown at this point, though he is not suspected of terrorist ties and was not on any watch lists. Robin told reporters that "[Lubitz did this] for a reason we cannot fathom right now but which looks like intent to destroy this aircraft."

The co-pilot had passed all medical and flight examinations, according to Lufthansa CEO Carsten Spohr. (Lufthansa owns Germanwings.) He was "100 percent fit to fly," Spohr said.

Why Lubitz did what he did remains the No. 1 mystery at this time, but there is another issue that merits investigation: how could the captain be locked out of his own cockpit? The captain, identified only as Patrick S. by authorities thus far, can enter a code from outside the cockpit to gain reentry; it is currently unclear whether he did this. But even if he had, the co-pilot could have "put the lever on lock," which would have blocked the code, according to Spohr.

The sequence of events, as heard on the black box, went like this:

  • The flight, Germanwings 9525, takes off from Barcelona on Tuesday bound for Dusseldorf, Germany.
  • Soon after, the captain goes over the flight plan with Lubitz.
  • The captain then exits the cockpit (we do not know exactly why as yet).
  • Lubitz then "manipulates the flight monitoring system to activate the descent of the plane," said Robin.
  • When the captain tries to return to the cockpit, he is denied entry.
  • At first he knocks lightly on the door, then progressively harder, but never gets any response from Lubitz in the cockpit.

Passengers onboard would probably have had no idea what was happening until close to the end. "Only towards the end do you hear screams," Robin added. "And bear in mind that death would have been instantaneous ... The aircraft was literally smashed to bits."

Investigations will continue, starting with the search for the flight's second voice recorder, which will provide information on the plane's instrumentation. Lubitz will also remain a primary target of inquiry, though to this point no one seems to be able to explain why he deliberately sent himself, five crew members, and 144 innocent passengers to their deaths.

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