Black boxes are a vital part of any investigation whenever a plane disappears or crashes - they record and store huge amounts of onboard data.
This information is key to figuring out what happened, but they're also often very challenging to recover.
When Air France flight 447 crashed into the Atlantic Ocean on 1 June 2009 it was flying from Rio de Janeiro to Paris, all 228 people on board were killed, including its crew of 12.
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It took a two-year search with incredible precision to eventually locate the wreck of the plane and recover its black box.
One of the harrowing parts of this discovery was the black box contained audio recorded from the plane's cockpit, letting investigators hear the last moments of the piloting team before the crash.
Captain Marc Dubois, 58, and his two co-pilots David Robert, 37, and Pierre-Cédric Bonin, 32, can all be heard panicking as the situation gets worse.
The black box revealed that the plane they were piloting, an Airbus A330-200, was having serious technical issues.
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Due to really adverse weather conditions, the plane's speed sensors - known as pitot tubes - had become blocked and iced up.
This caused the whole plane's systems to give the pilots incorrect data and also meant that autopilot wasn't working.
With confusing data about both altitude and speed coming through on their instruments, and little to no visibility, the pilots were essentially flying in the dark.
At a certain point, the plane apparently entered into a stall, and the pilots mistakenly pointed its nose up instead of down, attempting to fix this.
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This caused the plane to suddenly lose altitude and fall out of the sky, with the piloting crew's reaction caught on audio.
The transcript is fairly horrifying. One pilot exclaims: "We’ve lost our speeds!"
"I don’t know what’s happening," another concerned voice says, and Bonin can later be heard exclaiming: "Let’s go! Pull up, pull up, pull up!"
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As it becomes clear that there's no saving the plane, Rober screams: "F***, we're going to crash! It's not true! But what's happening?"
It took over four minutes for the plane to reach sea level, which must have been a completely horrific period of time as it went out of control.
Over a decade later, though, the data helped a court to reach the verdict that Air France and Airbus were not guilty of manslaughter for the deaths of all 228 people on board the flight.