The present invention includes improvements to cross-flow fans and cross-flow fan propelled aircraft including improved control, a dynamically adjustable vortex wall and internal housing, a vortex tube, vertical takeoff and landing rotorcraft configurations, the inclusion of an optimized oscillating blade fan, a wavy vortex wall, power plant refinements, dual leading and trailing edge configurations, stability improvements, tip plates, tapered wings, tapered fans, a fan construction method, and underwater applications.