WASHINGTON — The Federal Aviation Administration's lax oversight of aircraft maintenance at American Airlines raises concerns about the agency's ability to regulate airline maintenance in general, a government watchdog said.

Investigators confirmed at least four maintenance-related allegations made two years ago "have potential safety implications," according to a report by the Transportation Department's inspector general released yesterday.

At the time, maintenance problems at American were increasing, and the airline had experienced a 32 percent rise in delays of maintenance work, the report said. The airline went from an average of 298 open maintenance items to 394 open items, the report said.

Despite the increase, the FAA only tracked the number of deferrals rather than identifying the cause of the delays or the type of aircraft parts involved, the report said.

At the time, American also wasn't following required procedures for inspection of maintenance work, the report said. In one case, American didn't comply with a service bulletin alerting carriers to problems with windshield heating systems on Boeing 757s despite a warning that the problems could cause the windshields to crack or shatter if left uncorrected, the report said.

FAA and American officials say the problems are old issues that have largely been addressed.

American spokesman Tim Wagner said the airline's tally of delayed maintenance jobs has dropped sharply and is now below the industry's average for delayed work.

The carrier's "safety record and operational statistics prove that American Airlines maintenance practices are incredibly safe — amongst the best in the business," Wagner said.

However, the report said FAA is still working on some of the issues and the effectiveness of the agency's actions is "still uncertain."