A propulsion and lift system of a tiltrotor aircraft includes a wing having an outboard end, a wing tip assembly having an inboard end, a fixed nacelle coupled to the wing tip assembly and a wing-nacelle splice assembly having inboard and outboard sides. The inboard side of the wing-nacelle splice assembly is coupled to the outboard end of the wing, and the outboard side of the wing-nacelle splice assembly is coupled to the inboard end of the wing tip assembly, thereby coupling the fixed nacelle to the wing.