Airplane based laser systems for DIRCM, active imaging and communication are important applications attracting considerable interest. The performance of these systems in directions where the laser beam points close to or through the exhaust plume from the jet engines may be severely reduced. A trial to study these phenomena using a downscaled jet-engine test rig was carried out. The results on propagation of laser beams along and across the plume from these trials are presented. For laser beams propagation along the engine axis an OPO based source producing co-propagating laser beams at 1.52 and 3.56 μm was used. The beams were projected on a screen and imaged with separate IR cameras to study beam wander and spot degradation. Propagation across the plume was studied with a 532 nm laser projected on a screen and imaged by a high speed camera. The engine thrust and the distance between the engine nozzle and the laser beams were varied to study the effects of changing conditions. Scaling to full size engines and performance implications for DIRCM is discussed.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.