Some of the deadliest air crashes in history have been caused by simple misunderstandings, and it's a tiny error in the cockpit that brought tragedy to Quincy Airport in Illinois. Meanwhile, a minor mistake, a non-standard approach, and heavy smoke add up to a tragic misunderstanding that cost the lives of everyone on board Garuda Indonesia Flight 152. And, however disastrous, never has a misunderstanding taken as devastating a turn as on the island of Tenerife and the single deadliest aviation accident of all time.