WASHINGTON (CNN) -- The first phase of an audit by the Federal Aviation Administration shows that airlines are 99 percent compliant with mandatory air-worthiness directives, the agency's acting administrator said Wednesday.
Four U.S. airlines are under investigation for failing to comply with federal aviation regulations, Robert Sturgell said.
"The special audit that began March 13 showed us that the system we have in place is effective," he said at Reagan National Airport.
Sturgell noted, however, that improvements could be made, and said he is proposing several initiatives to strengthen the reporting role and regulatory process.
The audit began after the air safety watchdog ordered its inspectors to reconfirm that airlines are complying with U.S. regulations in the wake of revelations that Southwest Airlines continued to fly more than 100 aircraft without certain mandatory inspections.
"We had a breakdown in the system with Southwest Airlines. It was a two-way breakdown," Sturgell said without elaborating.
Sturgell spoke on the eve of a congressional hearing looking into the Southwest revelations. He and representatives from Southwest will testify at the hearing, along with two FAA inspectors who made the initial allegations and said that the agency was aware of the problems.
Every year, the FAA issues about 250 air-worthiness directives on more than 83 airplane and engine models, requiring airlines to correct potential safety problems, according to the agency's Web site.
According to Sturgell, inspectors examined almost 2,400 directives in the first phase of the audit, including those addressing maintenance programs, and found a rate of compliance of about 99 percent.
That makes this the "safest period in aviation history," he asserted.
The other 1 percent involved record-keeping errors and seven instances with four airlines in which compliance could not be established. He didn't list the airlines, saying the incidents are under investigation.
The audit, which involves 117 carriers, has been focusing on improving communications and tracking mechanisms, Sturgell said.
Among the improvements is a safety issues reporting system that will give inspectors and employees a "new avenue" for raising safety concerns, he said. The system will be in addition to the hot lines that allow administrators and employees voice complaints anonymously.
The new reporting system is to be in place by April 30, he said.
Nicholas Sabatini, the FAA's associate administrator for aviation safety, said the agency's inspectors found 34 discrepancies during phase one of the audit. Of those, 27 were resolved, and work is under way to resolve the others, he said. E-mail to a friend