A Continental Q400 with registration number: N200WQ, crashed into a house in the buffalo-area last thursday (14/2-2009), just 5 nauticalmiles from it’s destination.
50 people were killed in the crash, which might have been caused by a build-up of ice on the wings. This would have changed the wing profile, and forced the aircraft to stall.
A stall, in short, is the point of which the airplane moves to slow to fly, and starts to drop like a stone instead. Pilots are trained to coupe with this, but in low altitudes it can be dangerous or (like here) even fatal.
Aircraft have anti-iceing systems to prevent things like this, from happening. Apperently, the system weren’t working correctly, which is very rare though.