Usually there are health code considerations, such as wearing shoes, a shirt, etc, that should be enforced (remember the old "No Shoes, No Shirt, No Service" sign when entering places that serve food) but it is hard to say what the correct form of the clothes should be (e.g., coat and tie). In some cultures people use perfume to mask odors, other shower and apply deodorant, some do nothing at all (I think based on personal olfactory encounters) - which is right depends on your point of view.
I always try to dress nice on the plane, especially if I am in F/B because you never know who you might meet (the future ex-spouse, not that I have any experience in this at all), but I do love my TIN-TIN tee shirts too
[This message has been edited by beetee (edited 08-17-2000).]