Thats not how I remember them. Deregulation started in 78, the effects took a while, then you had several BKs in the 80s, 92-94 was also affected by the recession.'92-'94 and most of the '80's were generally good periods for the airlines, so I'd guess 15-18 years since deregulation (about 1/2 the years) but that's only a guess.
Jim