The Federal Aviation Administration routinely fails to determine whether violations it uncovers at aircraft repair stations are ever corrected, according to a new report by the General Accounting Office.

• Repair stations now do nearly half of the $6.5 billion in annual maintenance, repair and renovation work on airliners.

• Some 600 of the FAA's 3,000 inspectors are detailed to monitor about 2,500 U.S. repair stations.

• The report said the agency does not keep the proper paperwork for adequate follow-up inquiries once it discovers violations.

• The Congressional auditors said they had examined the records of 172 cases in which the FAA had sent letters to domestic repair stations -- but there was no response in the file to about one-quarter of the cases.

In one case, a shop failed to separate new and serviceable parts from those that were not serviceable. In another, work was being inspected by a mechanic rather than by a quality-control inspector.

The FAA began a process to update the regulation of repair stations in 1989, but has not finished it, according to reports.