Good suggestions so far. I occasionally travel by plane with a hard hat and PPE. Never found anything better than jamming into my normal bags. I mostly use an out of production ~60l Mountain Hardware roller bag. I have or have had Patagonia and Arcteryx bags; generally impressed. I wore out a great Boyt Company duffel after about ten years, I really wish I could replace that quality. Other thoughts - I have noticed the ASO bags in the D.C. area. Also would recommend London Bridge Tactical.