A U.S. Navy fighter jet crashed into the San Diego Harbor after two pilots ejected at around 10:15 a.m on Wednesday, Feb. 12.

Here are some of the reasons why aircraft can catastrophically veer toward the ground like a medevac jet did in Philadelphia on Friday night.

Here is a far-from-exhaustive list of some possibly relevant antecedents to Friday’s crash regarding why aircraft can nose-dive. At the time of the crash, the weather in Philadelphia was ...