Black boxes are officially known as flight recorders, and they basically act as a plane’s memory unit. The flight data recorder measures more than 1,000 different variables, including a plane’s speed, altitude and location. A voice recorder collects all conversations happening inside the cockpit. They often include an underwater locator beacon, as well, in case a crash happens over water.
These tools are designed to resist even the most extreme accident scenarios. Before they're installed, these devices are tested to withstand temperatures of 2000 degrees Fahrenheit for an hour, pressures found at roughly 20,000 feet below sea level and hitting a concrete wall at more than 450 miles per hour.
The Federal Aviation Administration has required all U.S. commercial aircraft carry black boxes since the mid-60s. U.S. laws are based on EU rules, which set minimum requirements for how much data the boxes collect.
But it's hard to say exactly why the recorders are called "black boxes." There’s some speculation that the term comes from WWII pilots, who used early versions that did come in black boxes. Other stories say the name comes from charring which can make the box appear black.
Legally, the recorders must be bright orange or yellow. The U.S. government set that rule in 1965, so that they're easier to find if they ever have to be recovered.
Additional reporting from Newsy affiliate CNN.