you assume that. I honestly wonder how it is possible if you are a sky watcher how you could have FAILED to see this before 1995. It is not as rare an occurance as you try to make it. contrails can persist for hours. Likewise, given the appropriate conditions contrails will rapidly spread out along the previaling wind directions and can lead to an overcast sky quite rapidly.

All easily explained by natural conditions - which were gone into in great detail when I was taking my meteorology classes back in the '70's; so the information is certainly still available.