It is extremely rare for a modern commercial airliner to crash solely due to turbulence, as aircraft are engineered to withstand forces far greater than those encountered in nature. However, it has happened in the past, most notably BOAC Flight 911 in 1966, which disintegrated near Mount Fuji due to "abnormal" mountain wave turbulence that exceeded the plane's structural limits. Since then, engineering and meteorological forecasting have advanced significantly. Today, turbulence is considered a major safety concern primarily because of injuries to unbuckled passengers and crew, rather than the risk of the plane falling out of the sky. While extreme turbulence can cause structural damage or temporary loss of control, modern pilots are trained to avoid severe weather, and the wings of modern jets are designed to flex significantly without breaking. The "crash" risk today is almost zero for commercial jets, though smaller, lighter aircraft remain slightly more vulnerable to sudden, violent atmospheric shifts.