Summary: GAO discussed the Federal Aviation Administration's (FAA) research on terminal doppler radar development and wind shear hazards, specifically: (1) the difference between the terminal doppler radar and the next generation weather radar (NEXRAD); (2) the status of radar development; and (3) other measures FAA can take to increase safety by minimizing the risk associated with wind shear. GAO noted that: (1) NEXRAD is a long-range radar used to identify severe storms as part of national weather needs, but will not address airport wind shear hazards; (2) the terminal doppler radar is a short-range radar used to detect small, low wind shears, including extremely violent, rapidly developing, vertical wind shears around airports; (3) the two systems have different technical requirements for cluster suppression, data updating, and automation; (4) FAA plans further research on the terminal doppler radar system; and (5) critical requirements may not be developed in time to add the terminal doppler radar to the NEXRAD program. GAO found that FAA should: (1) collect the necessary data to establish terminal doppler radar siting priorities; (2) test and evaluate a fully automated initial production system in an operational environment before controllers and pilots begin to rely on it; and (3) reexamine the system's technical requirements in an effort to reduce production costs and to increase the number of proposed installation locations.