This isn't PSA as PSA copied them as well:
https://en.wikipedia.org/wiki/Pacific_Air_Lines
Herb said his inspiration was PSA however I've always wondered if thats the whole story especially because of Southwest Airways original livery colors "coincidence" and the desire of SWA to perhaps camouflage being such a blatant knock off after also using the name and business model.
Southwest Airways (later Pacific Air Lines) is the origin of the no frills, low cost, quick turns, fun loving, light hearted persona discount airline business model. US deregulation was like an angel descending from heaven for Herb in 1978. Herb did it well and also had much better luck of timing.
The conversation isn't complete without the names Jack Connelly and Leland Hayward. They both passed away the year Southwest Airlines began operations. They have been all but forgotten in the shadow of SWA.