When I worked for Westinghouse, I'd fly to a job with an open return ticket, I could use whenever I was ready to come home. The rule was, if the flight I chose to return on, was full in coach, I could bump to first class rather than waiting for another flight.
Well, you know..... hey, I didn't make the rule..... look, I've been working 13 hours a day, 7 days a week, living in a motel room, for 10, 12 maybe 14 weeks..... I deserve it.
One time I flew first class from Chicago to Philly, on a 747, alone. Yup, just me and 4 stewardesses had both decks(floors) to ourselves. Also, Philly to Madrid and back, 747 first class, but not alone...... I only had 3 seats to myself.