To Derek at 09.52, the Air France 447 in 2009 crashed because the pilot tried to raise the nose, sending the plane into a stall, and causing it to plunge, pancake-like, into the ocean.
https://en.wikipedia.org/wiki/Air_France_Flight_447
In theory, a parachute might have saved this, but not in practice.
First, the parachutes on the space shuttle, or fighter aircraft (especially as they touch down on sea-borne carriers) are intended to decelerate the aircraft as quickly as possible,
after the craft has touched down on a runway.
They are not intended to prevent or mitigate a hard impact as the aircraft plunges from a considerable height.
It is true that he capsules containing astronauts (such as the Apollo missions), used parachutes to slow the impact, after the capsule had decelerated from supersonic speeds due to air friction. However, the capsules are relatively light and small and near-spherical in shape, in comparison to a large passenger aircraft.
Trying to arrange parachutes on a passenger aircraft that would keep the thing horizontal as it dropped would need (at least) three 'chutes arranged around the wings and the tail; they would need to be balanced for size. Not an impossible task, but not trivial.
And then what happens when the thing hits the ground? The impact speed would be enough to kill most of the occupants, ubless the 'chutes were impracticably large. In the case of AF 447 (above) the impact speed crushed almost everything on board, as it hit the ocean surface pancake-like. "The airliner was likely to have struck the surface of the sea in a normal flight attitude, with a high rate of descent"
In addition to the challenges of achieving a survivable ground-impact speed, I guess the main reason is that when aeroplanes are up in the air, they almost always have a large forward velocity (around 500 mph). If the 'chutes were deployed (by accident, for example) during normal flight, first, the windspeed would probably destroy the 'chutes and second the rapid reduction in forward speed would probably cause the aircraft to fall out of the sky, with no certainty that the 'chutes would remain effective as the relative wind-direction changed rapidly from near-horizontal to near-vertical (even if they remained undamaged due to the forward motion of the aircraft).
In short, a chute that is big enough to slow the dropping aircraft down to a survivable impact speed and also strong enough to withstand a 500mph-plus forward wind speed during deployment would be impractical.
Having said all that, flying remains he safest form of travel, so I wouldn't worry about it :)