Airplanes in Ash Clouds

When an airplane passes through an ash cloud it is disastorous for the passengers, pilots, and crew members. The ash can coat the entire windsheild, making it impossible for the pilots to see, but if the ash is sucked into the engines, it can cause the engines to stall out. This will essentially cause the plane to free fall. This has happened twice before, and the pilots were able to restart some of the engines and do an emergency landing. Here is a video clip that explains what is happening in England, and what exactly happens when a plane engine encounters volcanic ash.
http://link.brightcove.com/services/player/bcpid69900095001?bctid=78324298001