With large airlines, it's always about the money, and these are some things that their pilots aren't supposed to tell passengers. In commercial aviation, the first officer is the second pilot of an aircraft. The first officer is second-in-command of the aircraft, to the captain who is the legal commander. In the event of incapacitation of the captain, the first officer will assume command of the aircraft. In the rank of senior first officer the pilot will also sit in the right hand seat. Often the senior first officer position is used within airlines to mean someone who has passed all the requirements for captain, but there are no captains positions within the company as yet, and therefore they are "on hold" until a position as captain becomes available when they will receive their command line check. Continue reading for more.