Sorry if it wasn't clear, my comment doesn't just refer to aircraft but to all means of mass transportation, with units of USD per passenger mile. It's based on

Sorry if it wasn't clear, my comment doesn't just refer to aircraft but to all means of mass transportation, with units of USD per passenger mile. It's based on extensive analysis but is also pretty obvious when you think about it. Yes, as the passenger:pilot ratio gets high, other costs will exceed the pilot's salary. In the case of a Cessna 172 (for example), even if the pilot works for free, 25% of the vehicle's capacity is wasted, unless the pilot is also a passenger. This isn't true in the case of the general population so these planes aren't used for mass transportation.