Aircraft having multiple seating configurations and associated systems and methods are disclosed. An aircraft in accordance with one embodiment, for example, can include a fuselage having a generally circular cross-sectional shape and one or more passenger cabin portions. The individual cabin portions can include a floor connected to the fuselage and a plurality of passenger seats attached to the floor. The passenger seats are in a configuration selected from a first twin aisle seat-row arrangement and a second, single aisle seat-row arrangement. Each of the first and second seat-row arrangements is implementable in the fuselage. Further, the seats in either the first seat-row arrangement or the second seat-row arrangement have between a three abreast and a six abreast seating configuration.