Abstract: The invention relates to oil and gas production and can be used for lifting a fluid from a well by using a gas power. The inventive flying valve for a free piston comprises a tubular body, a detachable element, which is insertable therein and is embodied in a form of a solid of rotation, and an arrester used for limiting the detachable element travel. The arrester is embodied in the form of a ring, the diameter of which is less than the internal diameter of the tubular body and is arranged coaxially therein. The thickness of the walls of the annular arrester gradually increases in the direction of the detachable element and the top and lower edges thereof are rounded. The arrester can be embodied in one piece with the tubular body and connected thereto by means of one or more connecting straps. Said arrester can be also embodied in the form of a separate part provided with at least two fixing projections.