Where are you setting the bar for something to be commonly accessible?
Only about 60% of the world’s population has reliable access to clean drinking water. 18% of people own a car.
Compared to those numbers, 20% of people flying seems downright common - especially considering many people likely never fly simply because they have nowhere worth going (relative to cost).
That seems like it’s a pretty heavily “gilded only” type of thing especially if you look at percentage distributions of flight frequency and by class.