An aerial vehicle is described which comprises: a first compartment for holding a lighter than air gas; a second compartment for holding atmospheric air and having an inlet and an outlet; a solar panel for converting sunlight into electricity; a compressor for pumping atmospheric air through the inlet into the second compartment; control means for controlling the pitch and yaw of the vehicle; and a controller for controlling the buoyancy of the vehicle via the compressor and the outlet such that the vehicle is either lighter than the surrounding air and rising or heavier than the surrounding air and falling, and for controlling the control means such that the rising and falling motion includes a horizontal component. In another embodiment the solar panel is replaced by an engine and a fuel tank for storing fuel for the engine is also provided.The aerial vehicle can remain airborne for extended periods by using buoyancy propulsion.In the embodiments including a solar panel, a system including a light transmission station may be provided to supply energy to the solar panel from the light transmission station rather than relying on the incident sunlight alone.A method of flight using buoyancy propulsion is also described.