I'm usually changing hemispheres when I travel so I have to be aware of my destination.

I usually wear casual button-up shirt with pocket, dockers or jeans, light jacket, lace-up sneakers. I'm considering shorts in future because on flights where the air-cond has an impact there is usually a blanket included. It's rare for me to sleep on the plane so I don't have to worry about that. With spring/autumn flights I only have to worry about the chill during an early arrival time. When I arrive in a warm place I carry my jacket on top of my bag.

I usually take my shoes off in flight; I don't like wearing shoes and on the plane I don't expect to be walking on rocks or glass. I swap my socks for the supplied airline socks in place; no sense in in wearing mine out. If the bathroom has a wet floor from other travellers I'll either use another or I'll return to my seat for my shoes. The wet floor will be from the basin anyway. (As I don't sleep I don't have to queue with the other travellers to use the bathroom.) One flights of less than an hour I'll probably leave my shoes on.