In 1970, when I started flying to look at colleges, a one-way airline ticket between Philadelphia and Chicago was $55, or the equivalent of $382 in today's money. That was for coach, and coach service was good enough that you didn't really need to bother with first class unless you just wanted to do some conspicuous consumption or didn't want to associate with the riff-raff. Back then, even though wages and salaries were generally higher than they are now, these prices really meant that most people couldn't afford to fly, or more likely, they flew much more infrequently than they did now, unless they were flying for business. This was personally true for me; our family was pretty well off, but we hardly ever took a family vacation that involved airplanes. Most of the time it was "pack up the car, let's drive to Maine and rent a cabin." Come to think of it, we hardly ever ate out in restaurants, either.
I think airline deregulation was a huge mistake, specifically because it achieved its goal -- cheaper airline fares. That meant more people were flying, which has turned out to not be such a good thing for a number of reasons. First, of course, it means that the service you get on these cheap flights is lousy. You can get good service, but the fares are so high that most people just can't afford it. Second, is that the airports and planes are crowded, and the entire experience is much more unpleasant than it used to be. Third, service to smaller cities has been severely cut back. Finally, the vastly number of increased flights means more pollution, greenhouse gas emissions, and more transmission of disease as more and more people are traveling long distances. I've read that emissions from jet engines at the cruising altitudes of 30,000 ft. have a much more negative impact on air quality, global warming, and such than emissions on the ground.
Not to entirely pick on airplanes as a source of pollution. All transportation emits nasty stuff, and the world's increasing population means that even with technological improvements min emissions reductions, the emissions are going to increase. Probably if we're really serious about climate change, were going to have reduce mobility in general, but I can't see how that is possible in a democratic society. Maybe something like a carbon tax, riding the bad emitters will cost you more, but I'm not sure that Amtrak LD trains would fare so well, at least as long as they're being hauled by Tier 0 P-42s.