American Airlines defended its airport security system Friday after the government charged that federal agents carried explosives and a gun through the carrier's security checkpoints at Logan International Airport.

The government filed a lawsuit Thursday against the airline, seeking $25,000 in fines for 25 alleged violations of federal regulations.The lawsuit says that in June 1987, Federal Aviation Administration agents were able to pass through two separate American checkpoints at Logan with a dummy pipe bomb, hand grenade and gun packed in their carry-on luggage.

Al Becker, a spokesman for American Airlines at its corporate headquarters in Fort Worth, Texas, declined to comment on the lawsuit Friday. But he said American's security system "literally is the envy of the world."

"If you're asking me are we 100 percent perfect, the answer is probably not, because to operate a 100 percent perfect security system one would have to turn the nation's airports into armed fortresses."

A spokesman for the FAA's Washington office said such cases are usually resolved through administrative channels.

"Normally these civil penalties are paid by the airlines, not without protest, but eventually they're paid. It is unusual to have to refer the case to the Justice Department," said Fred Farrar.

The FAA does not release how often the security checks are conducted, but the latest figures available, for June through September of last year, showed a nationwide detection rate of 88.9 percent, Farrar said.

That means that 11.1 percent of the time, security agents miss potentially dangerous items, but that percentage is considered good.