40 years ago, I rode an AA 727-100 STL-LAX. Well, not quite. We lost oil pressure on #3, and diverted to TUL where a 727-200 was fresh out of the shop. The only reason for swapping planes was that the 727 couldn't make terrain clearance over the Rockies, should a second donk fail.
I remember the CC bitching that the -200 should have required one more FA, but AA didn't staff for that.