A quad-rotor or other unmanned aerial drone having a planar vapor chamber mounted to a processor of the drone to cool the processor. The processor may be enclosed in a protective central housing. The vapor chamber is mounted, in some examples, with a perimeter of the vapor chamber extending from the processor through the housing into an airflow region near the rotors of the drone so that airflow, which may include propeller wash, serves to cool the perimeter of the vapor chamber. The planar vapor chamber cools the enclosed processor using both phase-change cooling/heat spreading (i.e. heat is dissipated from the processor via evaporation and subsequent condensation) and convection (i.e. airflow passing over the perimeter of the vapor chamber carries heat away).