[gvr]

It might be better to include a parachute above the rotors.

The Cirrus SR22 single engine aircraft has this (their system's called CAPS.) It lets you sail to the ground in the event of some catastrophic failure preventing you from landing the aircraft safely. http://en.wikipedia.org/wiki/Cirrus_SR22

[mentos]

Would the airplane parachute be scalable to large commercial jets? I assume the fuel costs of carrying the extra parachute weight are too great but curious about the engineering.

[WalterBright]

Nobody has made a parachute remotely large enough. The engineering challenges are quite unknown.

I suspect the parachute would be far too heavy. Also, jets fly very fast, and the jerk when the chute opens would likely rip things apart.