the left. the conclusion of the british investigators was that each pilot did what the other pilot was instructed to do and the planes turned toward each other. >> reporter: at their closest point, the two planes were about 3 miles apart horizontally and 100 feet vertically. >> we got down to the last layers of protection. one pilot saw the other. >> reporter: the plane's automatic alarms alerted the pilots and they corrected their paths. former faa accident investigator steven wallace says it's rare four pilots get the instructions so wrong. but the safety nets kicked in and that, he says, should give comfort to airline passengers. he adds there hasn't been a collision between u.s. airliners since 1978. well, investigators remain the aa loss for answers as to why four pilots, two in each plane,