Abstract: An aircraft has a pair of wing portions with propellers of a propeller pair which are driven and synchronized by a fluid transmission between the power plant and the propellers. A fluid line structure keeps most components of the craft together and consists preferredly of three pipes which are also utilized to carry the driving fluid to and from the motors, to hold the motors and to hold the wings. The take over of a plurality of functions by the interior pipe structure reduces weight and secures safe and economic operation of the craft. The aircraft is provided with a propeller and motor arrangement that is retractable into a slot formed in the front portion of the wings.