The Federal Aviation Administration (FAA), in the wake of maintenance lapses at Southwest Airlines, is taking the unprecedented step of ordering a spot check of Boeing 737 maintenance records at all U.S. carriers.

The move means carriers with older Boeing 737 aircraft will have FAA inspectors check for compliance with certain structural inspections that were missed by Southwest and resulted in a record fine of $10.2 million for safety lapses.

Regulators do not suspect there are problems at other carriers similar to the ones uncovered at Southwest, but believe a broader review has merit.

“One carrier’s noncompliance with (safety directives) makes it necessary for us to validate our system for overseeing your management of this regulatory requirement,” FAA safety chief Nicholas Sabatini said in an e-mail to air carriers operating the Boeing twinjet.

The U.S. aviation agency said Southwest missed deadlines to inspect 46 Boeing 737s for structural flaws in 2006-07, and flew those planes after alerting the FAA about the oversight, but before it completed the checks. Small fuselage cracks were found on six planes and fixed.

Southwest subsequently launched an internal review of its records and found another lapsed inspection for fuselage cracks. It immediately grounded 38 planes; four were found to have cracks.

“While the data tell us flying is safer than ever, prudence dictates we take this additional precaution and conduct a special emphasis review,” Acting Federal Aviation Administrator Robert Sturgell said in a statement.

The FAA says “one recent failure to comply with one such directive” prompts the agency to make sure that all other carriers are in full compliance with safety rules. Sturgell said an initial review would be completed by March 28 and that the full audit would be completed no later than June 30.

Southwest says it is cooperating with the FAA and has stepped up its own safety checks. The airline put three employees on administrative leave after an internal review of its maintenance records.

The successful low-fare air carrier vows “to make any changes necessary to ensure that the airline is in full compliance with FAA airworthiness directives and all of its own maintenance programs, policies and procedures.” Southwest CEO Gary Kelley says “we have been a safe company. I believe we are a safe company. I am committed to making sure we become safer still.”

Meanwhile, the FAA remains under a microscope, with a supervisor transferred from the office overseeing Southwest Airlines. Sturgell says he is “looking at what went wrong, where we as an agency need to improve, discussing best practices, and finding ways to continually improve our system of safety oversight.”

Transportation Secretary Mary Peters has stated: “If any inspector failed in his or her responsibilities to the traveling public, they will be dealt with swiftly and severely. There is simply no margin for error when it comes to the safety of our aviation system.”

The FAA has spent the past two weeks answering for the regional supervisor’s decision to allow Southwest Airlines to keep flying jets that needed crucial safety inspections.

Within the past decade, the FAA has taken a partnership approach to regulation, relying on the airlines to self-disclose safety risks and de-emphasizes hands-on inspections.

In North Texas, for instance, inspectors chafed four years ago when the FAA decided to settle about 60 regulatory violations with American Airlines for $2.5 million, about $5 million less than the book value of the penalties.

More recently, FAA inspectors overseeing Southwest and Northwest airlines said they were removed from their jobs after trying to investigate serious maintenance problems at the carriers, allegations mostly supported by independent investigators.

The FAA’s maintenance oversight was also an issue in 2006, when a small airliner crashed into a shipping channel near Miami, killing 20. The operator, Chalk’s Ocean Airways, repeatedly fixed a fuel leak but missed the structural weakness that caused a wing to fall off.

After the crash, the National Transportation Safety Board recommended the FAA verify that maintenance programs of commercial airlines include criteria to identify systemic problems.

Ron Ricks, a Southwest EVP, said the airline’s recent lapses shouldn’t be used to indict the oversight system. The newer partnership approach has allowed airlines and the FAA to focus on fixing problems instead of assigning blame, he said. Under the old system, airlines were less willing to admit problems because they knew they would be punished.