In a last-ditch attempt to enter the cockpit, the pilot of doomed Germanwings Flight 9525 used an ax to try to break down the reinforced door moments before the plane slammed into the French Alps, reports said Friday.

The accounts added another dramatic and tragic image as Tuesday's tragedy unfolded: passengers crying out in terror as they realized the plane was on a collision course with the peaks, and the pilot desperately trying to override the apparent lockout measures of copilot Andreas Lubitz and regain control of the Airbus A320.

French prosecutors said the cockpit flight recorder was peppered with the sounds of the increasingly frantic banging on the cockpit door. And - as a chilling counterpoint - there was only the subtle sounds of Lubitz breathing after apparently setting the plane on a gradual descent into the mountains of southern France with 150 people aboard.

"Andreas, open that door! Open that door!' " the pilot yelled before reaching for the ax, France's private television channel Metropole 6 reported, citing French investigators.

The German newspaper Bild, citing security sources, also reported the pilot tried to slice into the door with an ax, which is part of the normal safety equipment aboard an A320.

But cockpit doors around the world have been made to near combat-grade strength since the 9/11 terrorist attacks.

The doors now have complex locking systems and reinforced materials that can include Kevlar, a fiber-weave built to resist gunfire.

On Friday, the parent company of Germanwings, Lufthansa, joined the growing list of airlines around the world requiring two crew members in the cockpit at all times.