The world’s worst air disaster occurred in 1977 on the Spanish Island of Tenerife. The accident which claimed the lives of 583 people onboard two Boeing 747s was attributed to a series of unfortunate coincidences and mistakes, the most heinous being the decision by one of the pilots to initiate an unauthorized takeoff on a runway where the second plane was taxiing. As a result of this accident, new rules were established for cockpit communication between pilot and first officer, which until 1977, allowed for a dogmatic style of command where the second officer was not permitted to challenge or second-guess any pilot decision. This, along with other changes, was immediately implemented in an attempt to prevent a similar catastrophe from recurring.