I love this bag for multi-mode travel. http://www.ospreypacks.com/en/product/gear_hauling/porter_46_1 http://www.ospreypacks.com/en/product/gear_hauling/porter

I love this bag for multi-mode travel. http://www.ospreypacks.com/en/product/gear_hauling/porter_46_1 http://www.ospreypacks.com/en/product/gear_hauling/porter_46... It meets airline carry-on requirements, but can be easily be slipped on and off in urban environments as needed. It probably won't work so well if you need to wear a suit jacket, but is otherwise great.