Special thanks to L-3 Communications, Aviation Recorders Division, for its help with this article.
On January 31, 2000, Alaska Airlines Flight 261 departed Puerto Vallarta, Mexico, heading for Seattle, WA, with a short stop scheduled in San Francisco, CA. Approximately one hour and 45 minutes into the flight, a problem was reported with the plane's stabilizer trim. After a 10-minute battle to keep the plane airborne, it plunged into the Pacific Ocean off the coast of California. All 88 people onboard were killed.


Photo courtesy U.S. Department of Defense
The cockpit voice recorder from the downed Alaska Airlines Flight 261, held by the robotic arm of the remotely piloted vehicle that retrieved it

With any airplane crash, there are many unanswered questions as to what brought the plane down. Investigators turn to the airplane's flight data recorder (FDR) and cockpit voice recorder (CVR), also known as "black boxes," for answers. In Flight 261, the FDR contained 48 parameters of flight data, and the CVR recorded a little more than 30 minutes of conversation and other audible cockpit noises.

Following any airplane accident in the United States, safety investigators from the National Transportation Safety Board (NTSB) immediately begin searching for the aircraft's black boxes. These recording devices, which cost between $10,000 an $15,000 each, reveal details of the events immediately preceding the accident. In this edition of HowStuffWorks, we will look at the two types of black boxes, how they survive crashes, and how they are retrieved and analyzed.