The FAA’s voluntary safety program, which protects U.S. airlines, repair stations and other aviation organizations from rule violations under certain conditions, for a second time will come under the scrutiny of the U.S. Transportation Department’s Office of Inspector General (OIG).

Starting Sept. 19, the OIG will launch an audit of the FAA’s voluntary disclosure reporting program (VDRP) to determine if the incident disclosures meet the agency’s requirements for protection from legal action and public disclosure. The audit, which is expected to take 10-12 months to complete, was mandated as part of the four-year FAA funding bill signed into law in February 2012.

Questions about the validity of the program emerged less than a year after the FAA rolled out the program in 2006, when whistleblowers disclosed VDRP abuses by an FAA principal maintenance inspector (PMI) and Southwest Airlines.

In the OIG investigation that followed, officials found that the PMI had “permitted and encouraged” Southwest to submit a VDRP filing for missing the due date on fuselage crack inspections for a large number of Boeing 737 classic aircraft, as required by an airworthiness directive (AD).

“[Southwest Airlines] made the disclosure and indicated that it came into the compliance with the AD, meaning it had inspected or grounded all of the affected aircraft,” the OIG said in its December 2008 report. “In fact, the airline had not done so, continuing to operate the aircraft for eight days after the carrier had notified FAA.”

In all, Southwest operated 146 aircraft on 1,451 flights carrying 145,000 passengers during the eight days, said the OIG, adding that five of the aircraft were later found to have fuselage cracks. The FAA proposed a $10.2 million fine to the carrier, but ultimately settled for $7.5 million on the condition that Southwest complete 13 safety-related improvements.

VDRP is among a handful of voluntary programs that the FAA uses to advance safety standards will affording protection for those you provide information.

“While [VDRP] provides an important opportunity to identify and mitigate safety issues that might not otherwise come to the agency’s attention, it also requires close monitoring by the FAA to ensure the program is not misused,” says the OIG in its announcement of the audit.

To receive protection from enforcement actions, an organization must notify the FAA “immediately” upon finding out about an infraction and before the agency learns of the issue “by other means.” In addition, the error must be shown to be inadvertent, and the company must take immediate action to fix the problem with a comprehensive solution.

As required by the FAA funding bill, the OIG is charged with determining whether the FAA ensures that air carrier disclosure reports meet entry requirements before being accepted into the program, and whether corrective actions air carriers have implemented to close out the incidents were effective.