[Hint: it's not the above.]
For years, and I mean YEARS, of pretty much monthly travel, I've been boggled at what people decide is appropriate to wear on airplanes. Just absolutely boggled. The sweatpants and the stiletto mules (often on the same person), the jeans that are more holes than jeans (with matching holey t-shirts), the ratty flip-flops, the micro-minis. I could never figure it out, until last night, while waiting for the red-eye home to Chicago from SFO, I had a little epiphany, or perhaps a little interlude of sleep-deprivation. (So hard to tell the difference, really.)
My take is that people who wear clothes on airplanes that are better suited to washing a series of strangers' cars at $5/pop have essentially given up all hope that they will ever be the recipient of happy chance. They've decided serendipity is not for them, so they've forsaken the notion that perhaps one day they may need to make a good first impression on a stranger. (They've also decided that they don't ever need to be upgraded to business class, never mind first.)
Me, I won't get on a plane in anything less than I would wear to a business-casual meeting. Usually a skirt + cardigan, mostly a skirt + comfy jacket. At least two pockets are essential, so I don't have to keep digging in my bag for ID & boarding pass. Flat shoes that slip on and off easily are a must, so that I can play my walk-through role in the TSA's security theater with aplomb. (The next time I'm behind someone in strappy, multi-buckle gladiator sandals, though, I'm tossing THEM to the lions.) If I'm flying on Saturday, *maybe* I will wear sneakers, but they're nice one, not the ones I use for mowing the lawn.
This way, if I end up sitting next to someone interesting, I don't have to shout over what my clothes are saying. Last night I saw clothes that said "I model for Frederick's of Hollywood, Lamé Division"; clothes that said "my favorite Saturday morning cartoon and a bowl of chocolate-frosted sugar bombs are what I REALLY need right now"; and clothes that said "I can change the oil in my car — and recently have." None of those clothes said "Take me seriously, please."
I'm not against comfort — notice I said "flat shoes, comfy jacket" and I wear t-shirts, for sure, not fussy silk blouses — but there's a line between 'comfortable' and 'raggedy-ass lazy' and the airport is not the place to cross that line. An airplane is a confined space, and, like any confined space, demands MORE civility and regard for others, not less.
So, please: no more flip-flops (and if you do wear flip-flops, please try to keep track of them, so that we aren't all held up on deplaning by you searching under three rows of seats for your left one). Try for clothes that have structural integrity; turbulence can be rough, you know? And I know they sell perfume (cheap, too!) in the airport, but that doesn't mean you get to try on five different ones before you board.
Before you leave for the airport, look at yourself in the mirror, and think: Could I meet and IMPRESS someone who would change my life while wearing this? And if the answer is "No," change. And add a sweater: those planes can get cold.