High fashion is always copying what the regular unfashionable people on the street are wearing, in the eternal search for authenticity.
Which is why things like bubble jackets, sweat pants, crocs and dad sneakers evolved from being laughed at to being very fashionable.
That's kind of what fashionable means.
Oxford dict:
Fashionable - characteristic of, influenced by, or representing a current popular style
I kinda like this Cambridges definition[1] of fashionable more (even if isn't perfect)
> wearing clothes, doing things, and going to places that are considered stylish
There is clear difference of what is considered stylish and what is popular.
Macmillian[2] has even more poignant definition available:
> popular with rich and successful people, and often expensive
Which I might disagree on specifics, but it still carries the thought over. Fashionable is not (necessarily, or even commonly) popular with the common people, but of some sort of elite.
[1] https://dictionary.cambridge.org/dictionary/english/fashiona...
[2] https://www.macmillandictionary.com/dictionary/british/fashi...
A lot of what is "popular" is still recognized by the wearer themselves as not fashionable, and is worn despite that (and sometimes because of that) for various reasons.
P.S. class aside, nylon is a bad choice to wear on an airplane. It melts into your skin. Cotton and leather are good choices if you want to survive an accident. Also decent lace up shoes can save your life if you need to exit a burning airplane. Try running over burning wreckage with flip-flops.
I take off my shoes for comfort when at altitude, but lace them up for takeoff and landing.