The Joint Center for Satellite Data Assimilation (JCSDA) was established by NASA, NOAA and the DoD in 2001. The goal of the JCSDA is to accelerate the use of observations from earth-orbiting satellites in operational numerical analysis and prediction systems for the purpose of improving weather forecasts, improving seasonal climate forecasts and increasing the accuracy of climate data sets. As a result the assimilation of AIRS data into operational Numerical Weather Prediction (NWP) systems and the assessment and optimization of their impact is a priority for JCSDA. Initially 324 channels of synthetic AIRS data were distributed from August 2001 to allow NWP Centers to set up and test systems to receive and assimilate the hyper-spectral data. In October 2002 the synthetic data were replaced by real observations from the AIRS instrument. A high priority activity of the JCSDA was to establish a fast Community Radiative Transfer Model (CRTM) for all AIRS channels. The CRTM model developed was OPTRAN8 and this was completed and tested pre-launch. The AIRS data has been used subsequently in the Global Data Assimilation System (GDAS) and ƒv SSI DAS for a number of parallel impact trials and data sensitivity studies. The initial GDAS studies have used the data available in real-time to the global operational communities. These have a spatial density of one in eighteen footprints and contains a selected subset of channels which well describe the spectral information content of the instrument. In initial studies, the spectral channels which were determined to be clear were assimilated. This paper describes these initial studies, noting the impact of the AIRS data on analysis and forecast skill. It will also describe recent data assimilation studies where data are used at higher spatial and spectral resolutions. In these studies the use of cloud free radiances, reconstructed radiances and cloud-cleared radiances will be examined.