Summary: In recent years, GAO and others have reported on vulnerabilities plaguing the nation's aviation system, the availability and limitations of explosives detection technologies used at airports, and efforts under way to improve aviation security. Terrorism was initially considered a possible cause of the 1996 crash of TWA Flight 800 and helped focus national attention on the system's vulnerabilities. The President formed the White House Commission on Aviation Safety and Security following the crash, and later congressional hearings highlighted continuing weaknesses in the U.S. aviation security system. Although terrorism has been since ruled out as a factor in the crash of TWA Flight 800, ensuing studies found that weaknesses persist. The Federal Aviation Administration (FAA), other government agencies, and the aviation industry are now implementing 31 of the Commission's recommendations on aviation security. Some of these recommendations are similar to legislative mandates that Congress enacted under the Federal Aviation Reauthorization Act of 1996. This report provides information on (1) the tracking, monitoring, and coordinating activities undertaken by the agencies responsible for implementing the Commission's recommendations and (2) FAA's progress in implementing eight of these recommendations, five of which are similar to mandates contained in the Reauthorization Act of 1996.