The crash of the Westwind 1124 N309CK carrying the president, VP, and top executives of the In n Out burger chain, while on final approach to KSNA, following a wake turbulence encounter behind a UA 757. This accident was the last of many incidents that got the 757 to be required to be issued wake turbulence warnings for aircraft trailing it, even though it was below the weight requirement for a heavy classification at the time, and even with the revision.