system
Given the following post, respond as if you're commenting on Reddit:
human
Dumb Question: Why can't airplanes be fitted to huge (~ mile wide) parachutes to slowly come down to the ground in case of an emergency?

From a physics standpoint, a large enough parachute to withstand the weight can probably be made.  Even if it slows the plane down just a bit, it could save lives. I'm sure there is a reason this hasn't been done, but I'm just not aware of any.
gpt
Because for most all airplane crashes, it wouldn't help. Very rarely is a plane somewhere out over the desert when suddenly "boom!" all power is lost and it starts plummeting towards the ground, everything else in tact. 

Airplanes normally crash during takeoff, landing or due to catastrophic failure. During takeoff and landing, the plane is too close to the ground for a parachute to work. During catastrophic failure, who is to say that the parachute would still work? Also, you can't just deploy a huge parachute, it would have to be a complicated system of drag chutes to slowly slow the airplane down. If the plane is spinning, well good luck. 

Ejection systems from fast moving objects are a topic of research. But the fact is, when you are moving that fast, it is hard to get down safely. Fighter pilots have to train for it, astronauts have a very elaborate evacuation procedure, but it only works for the smallest of time windows. If it were as simple as a parachute, it would probably be installed.