An unmanned aerial vehicle (00, 100', 100", 200, 300, 400) comprising: a body that is substantially toroidal and defines a duct with an upper end and a lower end that is opposite to the upper end, wherein the duct has an inner diameter that flares at the lower end; an electronic controller housed within the body; at least one electric motor that is controlled by the electronic controller; at least one fan within the duct that is operatively coupled to the at least one electric motor for rotating the at least one fan and creating an airflow into the upper end of the duct and out the lower end of the duct for creating thrust, wherein the at least one fan includes a first fan and a second fan configured for counter rotation; and a flight-control system configured to receive instructions from the electronic controller, the flight-control system including at least two flaps installed on the body and configured to redirect the airflow at the lower end of the duct, the at least two flaps each being moveable between a retracted position, wherein each flap is retracted into the body, and a protruding position, wherein each flap protrudes out from the body and into an area of the duct adjacent the lower end and based upon the received instructions, the flight-control system is configured to move each of the at least two flaps between the retracted position and the protruding position for controlling roll, pitch or both of the unmanned aerial vehicle (00, 100', 100", 200, 300, 400) during flight, wherein in the retracted position, at most only a portion of each of the at least two flaps is exposed and the portion is substantially flush with the body. a body that is substantially toroidal and defines a duct with an upper end and a lower end that is opposite to the upper end, wherein the duct has an inner diameter that flares at the lower end; an electronic controller housed within the body; at least one electric motor that is controlled by the electronic controller; at least one fan within the duct that is operatively coupled to the at least one electric motor for rotating the at least one fan and creating an airflow into the upper end of the duct and out the lower end of the duct for creating thrust, wherein the at least one fan includes a first fan and a second fan configured for counter rotation; and a flight-control system configured to receive instructions from the electronic controller, the flight-control system including at least two flaps installed on the body and configured to redirect the airflow at the lower end of the duct, the at least two flaps each being moveable between a retracted position, wherein each flap is retracted into the body, and a protruding position, wherein each flap protrudes out from the body and into an area of the duct adjacent the lower end and based upon the received instructions, the flight-control system is configured to move each of the at least two flaps between the retracted position and the protruding position for controlling roll, pitch or both of the unmanned aerial vehicle (00, 100', 100", 200, 300, 400) during flight, wherein in the retracted position, at most only a portion of each of the at least two flaps is exposed and the portion is substantially flush with the body. at least one fan within the duct that is operatively coupled to the at least one electric motor for rotating the at least one fan and creating an airflow into the upper end of the duct and out the lower end of the duct for creating thrust, wherein the at least one fan includes a first fan and a second fan configured for counter rotation; and a flight-control system configured to receive instructions from the electronic controller, the flight-control system including at least two flaps installed on the body and configured to redirect the airflow at the lower end of the duct, the at least two flaps each being moveable between a retracted position, wherein each flap is retracted into the body, and a protruding position, wherein each flap protrudes out from the body and into an area of the duct adjacent the lower end and based upon the received instructions, the flight-control system is configured to move each of the at least two flaps between the retracted position and the protruding position for controlling roll, pitch or both of the unmanned aerial vehicle (00, 100', 100", 200, 300, 400) during flight, wherein in the retracted position, at most only a portion of each of the at least two flaps is exposed and the portion is substantially flush with the body.