The so-called “black box” is one of the most important pieces of forensic evidence following a plane crash. There are actually two of these remarkably sturdy devices.

What is a black box, what can it tell us, and have the data recorders been found from Flight 5342 and the Army's Blackhawk?

A commercial plane with 60 passengers and four crew members on board collided with a military helicopter with a crew of three near Washington, D.C., on Wednesday night.