Air vehicle with a propulsion system that comprises at least one differential velocity fan, housed in and eccentrically arranged in a fan housing, which differential velocity fan comprises a rotor hub, to which fan blades are attached such that they stretch mainly radially out from the rotor hub, and at least one power unit and at least one power transmission device for transferring power from the power unit to the differential velocity fan; wherein the at least one differential velocity fan is arranged with its rotational axis perpendicular to the longitudinal axis of the air vehicle; wherein the differential velocity fan has a length, b, and a diameter D, such that b <=D; said air vehicle with a propulsion system further comprising at least one forward air duct and at least one rear air duct to lead air from air intakes (5, 16) rearwards in the air vehicle through at least one jet nozzle; wherein - in front of the differential velocity fan there is a plug that acts as a stream divider and prevents pressure drops and thereby reduces losses, - a part of the air that enters through the air intakes (5, 16) is passed via the at least one forward air duct into and axially towards the at least one differential velocity fan, - the side of the differential velocity fan between the rotor hub and outwards to the outer periphery of the blade is open so that the air has free passage into an open part of the fan rotor between the fan blades, - the air vehicle further comprises separating wall/disc between left and right side of the differential velocity fan, which prevents air from passing between the differential velocity fan's right and left sides and ensures that the air is pushed out radially from the differential velocity fan by preventing cross flow and that air that doesn't go into the differential velocity fan -spillover -flows further back and passes out through the opening and through the jet nozzle along with the air that has passed through the differential velocity fan, wherein in the rear air duct the speed of the air successively increases by the successively decreasing of its cross section and the static pressure decreases, and a portion of the air is forced out through an opening on the upper side of the air vehicle and gives an energized airflow on the upper side of the air vehicle while the bulk part of the air passes through the jet nozzles, each of which is regulated by a nozzle flap/spoiler and an upper nozzle flap and then said nozzles generates thrust by the passage of air from the at least one differential velocity fan. - in front of the differential velocity fan there is a plug that acts as a stream divider and prevents pressure drops and thereby reduces losses, - a part of the air that enters through the air intakes (5, 16) is passed via the at least one forward air duct into and axially towards the at least one differential velocity fan, - the side of the differential velocity fan between the rotor hub and outwards to the outer periphery of the blade is open so that the air has free passage into an open part of the fan rotor between the fan blades, - the air vehicle further comprises separating wall/disc between left and right side of the differential velocity fan, which prevents air from passing between the differential velocity fan's right and left sides and ensures that the air is pushed out radially from the differential velocity fan by preventing cross flow and that air that doesn't go into the differential velocity fan -spillover -flows further back and passes out through the opening and through the jet nozzle along with the air that has passed through the differential velocity fan,