Whenever a massive air disaster happens, there's always a huge investigation, and if salvage teams are able to find the flight recorder, they can learn far more about what actually happened.
These reveal extensive flight data to show how and where the plane went before crashing, but also sometimes include recordings of cockpit audio for insight.
That audio can be harrowing, as it was in the case of the single deadliest plane crash in history involving only one aircraft: Japan Airlines Flight 123.
In 1985 it crashed with a staggering 520 fatalities and, even more amazingly, four survivors - and the cockpit audio recovered from its wreckage is heart-rending.
Posted to Reddit a few years ago, it got a lot of attention and has multiple really affecting sequences, including audio of the moment that the pilots first realise that something has gone wrong.
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These pilots weren't at fault in any way, either - the plane had a catastrophic failure of its tailfin, which broke apart after suffering damage more than multiple flights earlier in a tailstrike incident that caused tiny structural issues that would get worse over time.
The failure caused a small explosion that severed hydraulic lines in the plane, effectively robbing its pilots of most of their controls.
The pilots can be heard trying to work out what has gone wrong and telling all the passengers to remain in their seats with their seatbelts fastened.
From this point, the pilots managed to keep the plane in the air for around half an hour, but with limited control over their flight path they ended up over some mountains in Japan, and eventually were unable to prevent the plane from crashing.
As the recording unfolds, you can hear the pilots' desperation getting worse as they fight to keep the plane in the air, holding off the risk of stalling and attempting to stay level, but they can't manage forever.
In fact, as part of the investigation into the crash, other pilots were put in simulators with the same conditions applied, and none of them were able to keep the plane in the air - showing how challenging the situation was.
When the plane crashed it took some hours for rescue crews to make it to the remote mountain location, by which time only four survivors were left, although they were successfully rescued. Sadly, it's been established that a quicker start to the search for survivors from authorities would probably have saved the lives of some other survivors who died before they were found.
Because the plane had been in crisis for so long, many passengers had written notes to loved ones that they put in pockets or bags, meaning that some family members got farewells and heartfelt messages.