An unmanned aerial vehicle comprising a rotor having one or more propeller blades and a propeller guard surrounding the rotor. The propeller guard comprises a main guard surrounding the one or more propeller blades and a movable guard vertically displaced from the main guard. The movable guard is movable from a default position to an engaged position by temporarily deforming the movable guard such that the movable guard contacts and obstructs rotation of the one or more propeller blades.