The National Transportation Safety Board determines that the probable cause of this accident was the flight crew members' failure to use available cues and aids to identify the airplane's location on the airport surface during taxi and their failure to cross-check and verify that the airplane was on the correct runway before takeoff. Contributing to the accident were the flight crew's nonpertinent conversations during taxi, which resulted in a loss of positional awareness and the Federal Aviation Administration's failure to require that all runway crossings be authorized only by specific air traffic control clearances.