Laser beam propagation in severe environment such as a jet engine exhaust may influence performance of e.g. laser countermeasure and active imaging systems located on airborne platforms. Beam propagation in close vicinity to the engine plume causes performance degradation due to beam wander and beam broadening effects. In this study beam propagation effects were studied experimentally using a downscaled jet engine. Beam wander and broadening effects were studied directing a 1.55 μm laser beam parallel to the jet exhaust. The beam centroid motion increased significantly during onset of the engine. Perturbation effects were registered imaging a blackbody source using a fast infrared camera. The geometrical set-up and thrusts were altered during the experimental registrations to examine various flow conditions. A comparison of experimental results with simplified theoretical models describing propagation close to jet engine plumes will be presented. Limitations in existing models will be discussed and methods for refinements proposed.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.