it's a free country, dress however way you want, within reason. I like to go with a nice looking t-shirt, slacks, and sneakers, and sometimes a windbreaker jacket. Same outfit I wear for intl F, domestic F. Just dress sensibly and you'll be fine.

Try not to smell too bad, and leave a little bit of booze for the next guy.

While in general, I'm a big fan of "wear whatever you feel like and who cares" if you're young enough you've got some concerns about THAT part, wearing things that are a little more conservative and formal than you'd otherwise be inclined to is a good way to look a bit older.

Why on Earth would you want to look a bit older? You'll have plenty of time for that later in life.

'twas handy, long long ago, for reducing the odds of getting carded.

Other than that, I can't see why either, but try lacking a time machine there's not much way to argue with my 17 year old self about it :)

Not always.

School uniforms are conservative and formal, and someone who is wearing them would not be mistaken for a graduate. What is the policy of private and public schools about wearing their uniform out of school?

Good point. I'd add a "usually" to the conservative and formal in that case, but ... yeah.

Very little idea on that, although I thought one of the excuses for uniforms at public schools in places like SoCal was to avoid attracting gang attention on the way to and from.

More generally, the uniforms (both public and private) I've seen have not generally been confusible with something anyone would wear voluntarily, either formal or casual. It strikes me that that the only time that's likely to be an issue when traveling by air is for a school trip... and if you're on a school trip in J or F... well... dang, that's one posh school.

It's a funny twist of history that Karl Marx' "dictatorship of the proletariate" and the "classless society" are so profoundly expressed in US American dresscodes and have become one of the country's best cultural export articles.
From Levi's via Nike to Ed Hardy ... :mad:

Unaesthetically dressed guests should be thrown out of any first class or real luxury hotel ...

Every stupid discotheque does it, but airlines and hotels didn't have the guts to enforce dresscodes. I am sure it was a mistake in the long term.

my wife and i, dressed in some of our finest casual blue jeans were blocked by the doorman at the Paris Ritz. all we wanted to do was go to the gift shop to buy calendars.

OK, good example.

If US domestic F were luxurious, i could see this, but....

I'm glad you don't ask for the two Glenlivets, that improves my odds of getting them. Otherwise we can fly AF where huge litre bottles of Glenlivet are their standard and they pour very generously.

I always make sure to wear white tie and my monocle when traveling by airship.

I don't know when the last time you went out to discotheque's was, but enforcement of a "dress code" as you think of it is a thing of the past. Most of the "coolest" places now don't want people who look well dressed in the FT sense of the word, and they certainly don't require it. I see MUC as one of your locations...for example, go survey the crowd at any random night at the P1.