Aviation
The Cajon Pass area is known for high wind, turbulence and fog. The weather over the pass can vary, from foggy days with poor visibility to clear afternoons where aircraft are bounced by gusting Santa Ana winds that top 80 mph (130 km/h). The wind in this area is predominantly out of the west, although in Santa Ana and other weather conditions it may be out of the north or the southeast. Air spilling over the San Gabriels can cause fairly violent up- and downdrafts. On a normal day, with the wind out of the west, turbulence usually starts a few miles west of Rialto and continues a few miles to the east, growing in strength above the altitude of the mountains and especially over the pass itself near the HITOP VFR intersection. In Santa Ana conditions, up- and downdrafts can become especially violent northeast of Ontario Airport, and turbulence can be experienced all the way east to the Banning Pass (itself known for turbulence.) It's important to note that the mass and wing loading of an aircraft determines its sensitivity to turbulence, so what may seem violent in a Cessna 172 may seem only mild to moderate in a Boeing 747. In the 2006 Mercy Air 2 accident, an air ambulance helicopter collided with mountainous terrain near the pass in foggy weather.
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