The only event I know of where that new policy played a central role was in the 2015 disaster in which a suicidal pilot locked the cabin while his co-worker too

The only event I know of where that new policy played a central role was in the 2015 disaster in which a suicidal pilot locked the cabin while his co-worker took a bathroom break, and crashed the plane: > "On March 24, 2015, the co-pilot of a German airliner deliberately flew the plane into the French Alps, killing himself and the other 149 people onboard. When it crashed, Germanwings flight 9525 had been traveling from Barcelona, Spain, to Dusseldorf, Germany. (history.com)" I believe there's now a strict rule of two pilots in the cockpit at all times as a result. Also, hijacked planes are now much more likely to be shot down by military jets if they approach urban areas, which is not a topic airlines like to discuss.