A collision avoidance system for aircraft. A light fixture assembly includes a housing with a base and a clear dome over the base. The base including an aircraft attachment element that allows for drop-in replacement of original light housings. An aircraft light is within the housing, as well as an ultrasonic sensor. The sensor is tied to a warning indicator configured to issue an alert when the light fixture approaches an obstacle. The installation provides a permanent replacement for wing lights or taillights, whereby the proximity sensors are always on the aircraft, and do not need to be added once landed.