As compared to dozens per year from 1968 to 1973, the total number for those years being 364. The numbers slacked off a bit after 1973 mostly due to (get this) an large increase in the number of armed air marshalls.
Wow. People with guns on airplanes makes flying safer. Who'da thunk it?
So, pre-1968 not that much to speak of. Some yes, but a drop in a bucket compared to post 1968.
"So, pre-1968 not that much to speak of. "
How'd I guess that you'd move the goal posts?