Don't forget the L-188 Electra. Eastern used them on the LGA-DCA-BOS Air Shuttle as main equipment and later as backup aircraft from the late 60's through the early 80's.
Eastern also operated Martin 404's along with CV-340's. Eastern wanted Martin to re-open the 404 production line, but couldn't get them to do it so they went to Convair for additional short/medium range capability.
They flew DC-7B's side-by-side with various models of the Lockheed Constellation.
Eastern traded their 720's back to Boeing for 722's in the late 60's and early 70's.
I was not aware that Eastern operated the DC-10. Can anyone fill me in on where they got them from and when and where they operated them?
Delta Airlines has the distinction of being the first major US airline to operate all 3 types of first generation widebody passenger jets. In the early 70's they briefly flew 747's, DC-10's and L-1011's. The DC-10's were leased from United until their own L-1011's were delivered.
If you want to see a really messed up fleet, you should check out Northwest (Orient) Airlines from the 40's through the mid 60's. If it flew, they operated it at one time or another.