Once upon a time, airlines flight were all one class. I believe it was in the 50's, before the jet era, that economy was added. In some aircraft, economy was in the front of the plane, where the noise was greater.
Most of the US majors had two cabin service through the 60's. Though I remember a UA ad that talked about three-classes on their 707's. Seating was either 2-2, 2-3, or 3-3. They didn't call the middle cabin business at the time.
At what point did the US majors add two class service to domestic flights?
I remember that airlines like PI and US were mostly one class, with a splattering of F flights on their longer routes.
NY was all Y.
PE was Y, except for their 747's.
RC had a C cabin on some planes, but no F
YX is all Y with F (ish) service.
WN and J6 are both all Y.
Did FL and WA offer F service? What about QF?