It's amazing all that goes into a plane crash. The very first passenger jet crash was caused by a faulty $12 light bulb, the 3 pilots were so distracted by the light bulb (which signaled when the landing gear was locked into place) that they did not notice that the auto pilot had benn turned off.

The plane was supposed to stay at 2000 feet but crashed into a swamp before the pilots realized they had lost altitude.