Abstract: Embodiments are directed to a high speed, vertical lift aircraft that has vertical take-off and landing (VTOL) capability and is capable of converting to a forward-flight mode (e.g., prop-mode). The rotors blades can be folded for high speed forward flight propelled by a turbine engine (e.g., jet-mode). The rotor blades on the tail sitter aircraft have a “stop-fold” capability, which means that the rotor blades are stopped in flight and folded back to reduce drag. This allows the tail sitter aircraft to achieve a higher speed than a tilt-rotor aircraft. In some embodiments, the tail sitter aircraft achieves both rotor-borne flight and jet-borne flight by having two separate engines. An additional advantage of the tail-sitter aircraft versus a horizontally oriented fixed engine aircraft is that supplemental jet thrust can be used for take-off if desired.