Back when I first started to fly them in the mid-70's from LBB to DAL they had Executive Class flights and Pleasure Class flights.
All the flights M-F from 6:00 a.m. (I think) to 6:59 p.m. were the Executive Class fares, from 7:00 p.m. and on, M-F, Pleasure Class fares. Then on the weekend, ALL flights were Pleasure Class fares.
Do you think an airline such as Southwest could still be profitable with just a two-fare type structure? Would it save man-hour costs in terms of filing all the differents fares to all the GDS services and their own website?