Abstract: A system for propelling vehicles for carrying passengers or cargo comprises a longitudinal duct, having a slit at the top and a pair of rails or tracks. A vehicle is provided to run on the tracks and has a fin which projects into the duct to substantially fill the same. Differential air pressure is applied to the duct to cause the fin to move along the duct and carry the vehicle with it. The duct may include several stations with means to produce differential air pressure between the separate stations. A braking device operates to apply brakes when the pressure on both sides of the fin is substantially the same. Preferably the vehicle contains no internal control for the fin or air pressure so that it can be controlled from the outside by the device for forwarding the differential air pressure.