An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation. The aircraft has an airframe including first and second wings with a fuselage extending therebetween. A propulsion assembly is coupled to the fuselage and includes a counter-rotating coaxial rotor system that is tiltable relative to the fuselage to generate a thrust vector. A flight control system is configured to direct the thrust vector. In the VTOL orientation, the first wing is forward of the fuselage, the second wing is aft of the fuselage and the coaxial rotor system is configured to provide thrust in line with a yaw axis of the aircraft. In the biplane orientation, the first wing is below the fuselage, the second wing is above the fuselage and the coaxial rotor system is configured to provide thrust in line with a roll axis of the aircraft.