Dallas ? A Federal Aviation Administration audit of U.S. airlines found that they had complied with airworthiness directions 98 percent of the time, the FAA said Friday.

“This audit gives us confidence that, overall, the system is safe and in almost every instance the airlines are complying with our safety directives,” Acting FAA administrator Robert A. Sturgell said in a statement.

The audit was prompted by several embarrassing revelations for the FAA, including the March revelation that Southwest Airlines Co. had continued to fly airplanes that should have been grounded until the aircrafts’ outer skin had been inspected for cracking.

In addition, American Airlines Inc. grounded its fleet of McDonnell Douglas MD-80s in April while it inspected and fixed wiring harnesses on the planes’ landing gear. The cancellation of more than 3,000 flights disrupted American’s schedule for days and affected hundreds of thousands of travelers.

The FAA said that in the 2 percent of cases where airlines were found not in compliance with the airworthiness directions or ADs, the issues were resolved before the aircraft returned to the skies.

The agency, whose work has been under investigation by a House committee, said the non-compliance fell into five broad areas:

¢ The carrier could not show compliance;

¢ The carrier needed additional records to prove compliance;

¢ The carrier had done the work but needed to get the FAA’s approval of an alternative means of compliance;

¢ The airplanes weren’t in compliance, but the airline wasn’t flying them; and

¢ “Other minor discrepancies” that didn’t involve airworthiness directives.

“All noncompliance issues were corrected before the airplanes flew again, and the FAA is investigating to determine if enforcement actions are warranted,” the agency said.

The FAA has proposed a $10.2 million fine against Southwest, and gave the Dallas-based carrier until last Friday to pay. Southwest told the FAA last week that it would not meet that deadline and was continuing to talk to the agency.

The FAA in August also proposed a $7.1 million fine against American for deferring maintenance improperly, deficiencies in its drug and alcohol testing and inspections of exit lighting. The proposed penalty was not related to the April problems.

Pushed by the Southwest problems, FAA inspectors from March 13 to 28 checked compliance with 10 airworthiness directives on each aircraft type at the 117 airlines they oversee. It said it questioned compliance in 34 cases.

In a second phase that ended June 30, FAA inspectors performed 3,236 audits and questioned the airlines’ compliance in 88 instances, the FAA said.

“Even with this tremendous level of safety and compliance, we have work to do,” Sturgell said. “We’re focusing on the language of our directives to make sure they are clear, concise and unambiguous, and we’re working with industry to approve work in progress before the compliance date.”