I work in the IT industry and when I travel I tend to wear a suit on meetings but most of my clients are on the casual side of business casual. My standard travel wardrobe is: suit, three shirts that match with the suit and can be work with jeans if needed, black loafers, two ties, and I usually travel in dark jeans, brown slip ons, and a polo or sweater. I am looking to branch out a bit though, and jeans are definitely not comfortable for a long red-eye flight.