I always go all-cotton these days. This usually means some kind of chinos, though I recently bought a pair of definitely not-SF-approved baggy-ish jeans that are supremely comfortable. As others have pointed out, you want shoes that are easy to take on and off - for me lately that has meant my 3-eyelet Rider chukkas. I'd love to go with slip-ons or loafers but I really don't ever wear them and every bit of "packing" I can do on my person I try to do, and the chukkas are supremely versatile. I do pack a pair of slippers in my carry-on and I have found that to be a tremendous luxury on the plane. I wear a button-up shirt, usually a zip cardigan (this is wool or cashmere) and a sportcoat that can take some abuse, sometimes cotton. I fly a fair amount of long-haul (US to China, US to Europe, typically ~4 times roundtrip/year) and this routine has served me fairly well. Pro tip - I always pack a small toilet kit and a real washcloth and either right before landing, or right after (before even claiming bags), I do a nice cleanup. Brush my teeth, wash my face, etc. Put the blazer and the decent shoes back on and after a long trip, you feel like a million bucks.
