one in a million experience that doesn't mean we can't learn from it and ensure this type of tragedy doesn't happen again. >> reporter: but it's not unprecedented. there are a handful of cases where ground crews have stolen planes. most recently, in may 2003, an aircraft mechanic stole a 727 airliner from angola. he and the plane were never seen again. as far as suicide by pilot, the most recent was german wings flight 9525. the captain was locked out of the cockpit. the copilot crashed into a hillside, killing all 150 people aboard. and suspected as a pilot suicide case, mh-370, the flight that mysteriously disappeared over the indian ocean. now there have been legislative steps regarding aviation employees there was a bipartisan bill tightening employee checks. it passed the u.s. house.