Data from the satellite lidar Geoscience Laser Altimeter System (GLAS) has provided a new means to retrieve height and optical depth of transmissive cloud and aerosol layers globally. We compare data sets from GLAS and an airborne under-flight of the Cloud Physics Lidar (CPL) during a unique smoke opportunity as part of a validation experiment in October 2003. The CPL has known layer identification and optical retrieval performance. GLAS data products, including calibrated attenuated backscatter profiles, layer identification, and optical depth, are compared to simultaneous aircraft lidar retrievals with similar model assumptions with a goal toward discovering algorithm biases in GLAS. The case described here involves heavy smoke layers from large-scale fires in southern California and thin cirrus clouds. The GLAS optical retrievals agree with the CPL data when the GLAS aerosol lidar ratio, S, is reset from default maritime to smoke and in inland urban pollution localities.