FAA's experience statements?
Jet J
Yes, with the exception of the airlines that were flying, Martins, Convairs or DC3's and the pilot hires that were less that twenty-one years old, all started in the backseat or middle seat as Second Officers. (ALPA didn't like the FE title) I'm sure there were some exceptions.
In most cases we had the progression of anywhere from five to twenty years experience prior to "checking out" as Captain.