Summary: The Federal Aviation Administration (FAA) issued 52 emergency revocations of operating certificates between January 1987 and May 1991 on air taxi or commuter operations; five were later overturned or reduced to a lesser penalty. No major airlines were issued emergency revocation orders during this period. Many of the revoked air carriers were established companies that had been in business for years. Air taxis accounted for 73 percent of the emergency revocation orders. The most frequent violations were for operating an aircraft in violation of the air carrier's operating certificate, operating unairworthy aircraft, and falsifying compliance records. FAA often learned of violations that led to emergency revocations during accident investigations or investigations done as a result of tips from employees, competitors, or customers, rather than as a result of inspections. According to FAA inspectors, key managers and owners who committed violations that led to nine emergency revocations returned to, or remained in, a similar position with an air carrier. Some of these individuals then committed more safety violations leading to another emergency revocation. While FAA lacks a formal system to track such key managers or owners, FAA plans to issue guidance by the end of fiscal year 1992 to inspectors on tracking key managers and owners.