Imagine 500m wide parachute. Would probably weight few tonnes, be very complex to deploy (say only above 1-2km altitude), very hard to inspect regularly etc. T

Imagine 500m wide parachute. Would probably weight few tonnes, be very complex to deploy (say only above 1-2km altitude), very hard to inspect regularly etc. The other problem is, a lot of death/damage is done after plane hits the ground and starts to burn. You wouldn't be able to prevent that, since emergency parachute falls are hard ones. So you might still end up killing everybody on plane.