Tangential issue:
30 yrs. ago I was booked STL-LAX on an AA 727-100. Crew did a precautionary s/d on #3 due low oil pressure. They couldn't tolerate a 2nd failure over the Rockies so we diverted to TUL (AA main base) to switch to a 727-200 just out of the shop.
Same crew all around. Same pax load.
But the cabin crew complained that the -200 required one more attendant.
(I don't recall if we got a new safety briefing, though...)