Black boxes—which are actually orange, not black, to aid in discovery—are remarkably resilient; they're built to withstand fires of 2,000 degrees Fahrenheit and an impact of 3,400 times the force of Earth's gravity, roughly a velocity of 310 mph
It's interesting that the black box from the Karachi crash survived and they were able to playback the last communications but no such luck with the 757 black box.
Imagine if we had a transcript of what happened on that 757.
