According to several reports on the tragic fate of the Germanwings Flight 9525, the captain who was locked out of the cockpit was trying to break down the door using an axe immediately before the aircraft crashed into mountainous terrain in the French Alps.
Along with sawn-off shotguns, sabres and cricket bats, axes are expressly forbidden as carry-on items for passengers.
The mere presence of an axe in an aircraft cabin could constitute a security threat, however Boris Ogursky, a spokesman for Germanwings' parent Lufthansa, has confirmed that their aircraft do carry axes.
According to Ogursky, axes are kept in the cockpit, and in the case of Flight 9525 the cockpit door had been locked by the co-pilot, and therefore the axe would have been out of reach of the pilot.
In the past axes were commonly carried as part of an aircraft's fire fighting equipment to enable flight crew to break through panels and sidewalls in case of an electrical fire.
Due to anti-terrorism regulations, most carriers have replaced their axes with crowbars which are insulated to protect against shock, however it seems that not all airlines have adopted the same policy.