No-fly zones are areas in Northrend where flying is not possible. These include the city of Dalaran and the whole zones of Lake Wintergrasp and Sholazar Basin. In them you can not mount on any flying mount, or shift into Flight Form. When entering one of these by fling, you will get a warning, and then get forcefully dismounted. You will get a parachute to prevent dying from falling on the ground, but if you are too high in the air the parachute will wear out and you can die nevertheless.