Fortunately I've never seen a fatal accident at an airshow, but some "That was v. close!" events:
- September 1986 at RAF Leuchars. An RAF Jetstream included a steep descent to a touch-and-go in the display. All went fine except that the landing flare was rather too low and the aircraft smote the runway quite hard, bounced into the air and staggered off back to Finningley.
- August 1987 at CFB Abbotsford. A CF-18 display nearly ended in tears after a max 'g' pull out resulted in a recovery well below 50ft agl. The rest of his display was cnx'd!
- July 2003 at Hradec Králové. Two MiG 29s put on such an 'interesting' display that we christened them 'The Dangerous Brothers'! A week or so later they collided at RIAT.
- August 1993 at RAF Alconbury. An F-111 came roaring in from the east with wings fully swept, rolled into a hard right turn and entered serious wing rock, almost departing. The Tornado mate with whom I was talking looked horrified. On the second display day the pilot used a more modest wing angle and didn't pull quite so hard!
- July 2005 at RAF Fairford. That infamous RAF Typhoon event!