My friends who are consultants (who fly out every Monday or Sun. and fly back every Thursday night – to the same client site in the same city every week for 45+ weeks a year) still have to get a ticket for each and every flight.
I’ve heard of them pre-arranging all the flights for a set price by calling the airlines directly and pre-purchasing all at once for a discount, but the flights are still individually booked.
There are very small commuter airlines (known now as local service airlines) that do fly from very small regional airports—like I know of Penair that flights out of Islip, NY (Long Island) to Boston..and those airlines will sometimes provide a “commuter book” of tickets..where you buy a series of flights for a set price. That’s about as close as you’ll come (as far as I know in the mainland US) to “unlimited” commuter travel by air. (But..there is still a ticket per flight..)
And, fwiw, for my job I fly about 70% of my working time—essentially at least 2 weeks a month, recently it’s been 3 weeks out of 4 (and have some colleagues that fly even more than me) ..and I still have to buy my tickets one flight at a time even when I’m going to the same client site over & over.