Reading all these rules and tips makes my eyes cross.
Life was a lot simpler prior to the deregulation of airlines in 1978.
You chose your airline based on its schedule and how much you liked its service.
You bought a ticket (paper original with a carbon copy receipt) choosing one of two prices, first class or coach, and selected your seat. Every airline had the exact same prices on all city pairs.
You went to the airport, walked to the gate, and boarded the plane. I could arrive 15 minutes before the flight and park next to the terminal with no fear that I would miss my flight. Or, I could arrive earlier and go the the Horizon Club (Western Airlines) and relax. I think the club cost $95/year.
There were no airline branded credit cards or points or promotions.
But, airfares were expensive and prop planes were noisy.