Port and starboard vessel's starboard side by green and its port side by red. Aircraft are lit in the same way. Port and starboard Port and starboard are nautical and aeronautical terms of orientation that deal unambiguously with the structure of vessels and aircraft. Their structures are largely bilaterally symmetrical, meaning they have mirror-image left and right halves if divided long-ways down the middle. One asymmetric feature is that on aircraft and ships where access is at the side, this access is usually only provided on the port side. To understand which is which, when a person is facing the bow on a
Port and starboard is the left-hand side and the starboard side is the right-hand side. However, port and starboard never change; they are unambiguous references that are "not" based on the relative directions of an observer, just as the cardinal directions of east and west do not change no matter the direction a person faces. The term "starboard" derives from the Old English "steorbord", meaning the side on which the ship is steered. Before ships had rudders on their centrelines, they were steered with a steering oar at the stern of the ship on the right hand side of the ship, because more