My morning newspaper today tells me why we board aircraft from the left. It is a naval tradition, they say, because the Greek and Phoenician triremes had a steering oar on the right, or steer-board side, so had to pull up to the dock on the left, or port, side. A nice story, but complete BS.
My reading of early aviation books tells me this: aircraft with rotary engines such as the Clerget suffered precessional yaw that made it difficult to turn right during rotation and takeoff. The preferred turn after takeoff was to the left. This meant that circuit patterns, even on all-over fields, were to the left. When side-by-side seating came along, the pilot sat on the left for a clear view into the turn and of the circuit. When airliners came along, the entry door was on the left so that the pilot could monitor boarding and confirm the door was closed.
So there!