Currently several networks of optical ground stations (OGS) are being planned and deployed for different space applications like commercial direct-to-Earth (DTE) optical communications, optical feeder links, satellite laser ranging and space debris collision avoidance services. To achieve their specific tasks, these stations typically uplink high-power non eye-safe laser beams across the sky. Laser beams can distract or injure pilots with temporary or permanent vision impairment and lead in the most critical cases to catastrophic events. This can pose serious threats to air traffic safety, when not addressed appropriately. This topic is highly relevant especially for the upcoming OGS networks which strongly benefit from autonomous operations without human presence for higher efficiency and quality of services. To this end a reliable system for aircraft detection deployed at each OGS is necessary to ensure safe operations and timely interruption of laser emission in case of predicted laser illumination of detected planes, helicopters and other manned flying objects. Transponder-based solutions offer a way for ground stations to monitor aircraft, but unfortunately today they cover only a part of the overall air traffic. In this paper a passive detection system based on multiple cameras operating in different spectral bands is presented. The detection algorithms developed make use of the collected images in the visible and different IR bands to identify laser beam-aircraft conjunctions and to automatically control OGS laser emission. An overview on the developed optical aircraft detection system and its performance will be presented. This technology complements existing methods of aircraft detection, offering broader coverage of monitorable targets and higher reliability to ensure safe OGS laser uplink operations.