The deranged co-pilot who deliberately flew a jetliner into the side of a mountain had a history of psychological problems and should have been on medical leave the day of the disaster
Investigators searching Andreas Lubitz's apartment in Germany reportedly found torn up doctor's notes, which he was supposed to use to take a sick day off.
Dr. Gary Kaye, a psychiatrist specializing in evaluating pilots.
INSIDE EDITION's Steven Fabian said to Dr. Kay, "Lubitz had these notes, doctors notes, excusing him from flying on this particular day, that Lubitz apparently ripped up and still went to work."
Dr. Kaye replied, "If you've received a medical note that says that you're not fit to fly, number one, you have no right in that cockpit!"
Lubitz had problems fitting in with other pilots who reportedly nicknamed him "Tomato Andy" because he had started out as a flight attendant serving meals.
He also broke up with his girlfriend recently.
Psychiatrist Dr. Gail Saltz told INSIDE EDITION, "Working with a team of people, it's hard to imagine that someone wouldn't have noticed something that was odd about behavior."
We're also learning more about the final desperate attempts by the pilot to save the plane. He actually tried to break down the locked cockpit door with a small axe.
When the plane's captain left the cockpit to go to the bathroom, his co-pilot locked him out. The captain could be heard knocking on the door to get back in, but got no answer. He started pounding on the door, but there was only dead silence. It went on like this for several agonizing minutes, and the passengers could actually be heard screaming as they realize the plane was going down.
The door can usually be opened from outside using a secret code. But the pilot can override that, as INSIDE EDITION's Victoria Recano found out at the Air Hollywood Flight Simulator in Los Angeles.
Rencano reported, "Normal protocol when a pilot is locked out of the cockpit, allows the pilot to enter a code opening the door within 30 seconds. But whoever is inside the cockpit can deny access by pushing a button, or by using the deadbolt.
The cockpit door is basically inpenetrable.
MIT Professor of Aeronautics and Astronautics John Hansman told INSIDE EDITION, "You would not be able to get through that door. Most of them are steel plated. Some of them are bullet proof."
In the U.S., there must be two people in the cockpit at all times. Now, in the wake of the tragedy in the Alps, airlines around the world are adopting the American regulation including Lufthansa, Virgin, Air Canada, Icelandair and Norwegian Air.
A lesson learned, but too late to save 150 lives.