Here is a video with some airplanes that use Dynamic Soaring to fly close to 400 mph
reach close to 400 mph without any propellers or motors.
Dynamic soaring is a flying technique used to gain energy by repeatedly crossing the boundary between air masses of significantly different velocity. Such zones of high wind gradient are generally found close to obstacles and close to the surface, so the technique is mainly of use to birds and operators of radio-controlled gliders, but glider pilots have occasionally been able to soar dynamically in meteorological wind shears at higher altitudes.
I initially thought they build up a "centrifugal force" and turn tightly to make the plane go faster.But it has nothing to to with any centrifugal force.