A buoyant aerial vehicle includes: a balloon configured to store a gas; a payload coupled to the balloon; and a propulsion unit coupled to the payload by a tether. The propulsion unit includes: a fuselage having a substantially longitudinal shape, a first end, and a second end; a primary airfoil coupled to the fuselage; a secondary airfoil coupled to the fuselage at one of the first end or the second end; and a thrust generating device disposed at one of the first end or the second end and configured to move the propulsion unit relative to the payload along a propulsion flight path. The movement of the propulsion unit imparts movement of the buoyant aerial vehicle along a vehicle flight path.