In the September 11 attacks , crew on one of the hijacked planes went beyond their scope of training by informing the airline ground crew about the events on-board . In separate phone calls , Amy Sweeney and Betty Ong provided information on seat numbers of the attackers and passenger injuries . This helped authorities identify them . As early as 1964 , the FAA required cockpit doors on commercial aircraft be kept locked during flight . In 2002 , U.S Congress passed the Arming Pilots Against Terrorism Act , allowing pilots at U.S airlines to carry guns in the cockpit . Since 2003 , these pilots are known as Federal Flight Deck Officers . It is estimated that one in 10 of the 125,000 commercial pilots are trained and armed . Also in 2002 , aircraft manufacturers such as Airbus introduced a reinforced cockpit door which is resistant to gunfire and forced entry . Shortly afterwards , the FAA required operators of more than 6,000 aircraft to install tougher cockpit doors by 9 April 2003 . Rules were also tightened to restrict cockpit access and make it easier for pilots to lock the doors . In 2015 , a Germanwings plane was seized by the official co-pilot and deliberately crashed . The European Aviation Safety Agency issued a recommendation for airlines to ensure that at least two people — one pilot and a member of cabin crew — occupy the cockpit during flight . The FAA in the United States enforce a similar rule
Germanwings plane
Germanwings Flight 9525
Aircraft hijacking