london, david diez, a former air branch investigator of the uk's department of transportation, robert mcfaden, co case agent. what normally happens when a commercial aircraft goes down for whatever reason, who's in charge, and what's the best practice for handling the site? >> >> well, here in the united states, if it's a non-criminal event, the ntsb is in charge of the investigation and is typically supported by the f.b.i., federal bureau of investigation. normally, there's two phases in the sense that the ntsb about be the primary investigative agency where we look at the power plants, the air frame, the operations, maintenance records, air traffic control records, we wanted to gather as much information and data to determine what possibly could happen to determine a probably cause. we gather all this information, both from the air carrier and most importantly from the scene. the sect part is really the victims. it's important to map out the location of where the victims are, coordinate identification of those victims and working with families in establishing a family systems center. all th