A somewhat mismatched look dictated by the circumstances:

Jeans (with no belt due to x-rays)
T-shirt
Comfortable long-sleeve shirt that looks slept-in, because it probably is
100% wool thin socks so my feet don't sweat
Slip-on black shoes that also go with my suit
Suit jacket

The shirt I'll wear for my meeting as well as the suit trousers are in my carry-on. Hopefully I have time to shower at hotel or lounge; if not I'll at least do the "touch no surfaces while changing" ballet in the airport washroom.

As is obvious from the above, I generally fly long-haul J, and very often it's a redeye heading straight to meetings on arrival.