If I am coming/going directly to/from a client site or one of our other offices, I'll wear dress slacks, dress shirt, and tie. Otherwise, it's usually jeans and either a button-down Polo shirt or a golf shirt, depending on the weather. For a flight to/from Europe, I'll pack a black t-shirt and long black workout pants and change once I'm on the plane. That's also the only time I'll take off my shoes on a plane, but I pack a second pair of clean socks.