From working the Midwest in the early 80's, I remember a couple of airlines that have not gotten a call yet in this thread:

Air One - This outfit was based in St. Louis and had the all FC configuration and service idea years before Midwest Express. They seemed to have the most attractive FA's in the business and I loved it and always tried to get it, but I think that the financing ran out in less than one year.

Britt - A commuter operation out of Southern Indiana (Terre Haute, I think). They used the oldest, rattiest, most second and third-hand planes that they could find, and my runs from IND to EVV were frequently pure adventure. It was axiomatic that Billy Britt never cleaned or fixed a plane if he could avoid doing so, but it finally caught up with him when two of them went down within a year of each other, and if memory serves, the Feds yanked his certificate.

Note to JerryFF - I don't remember Mo'-Agony,
but it sounds likely. When I worked upstate NY and Quebec in the 70's I called my territory "the route of the Slowhawk."