The five-foot tear in the roof of a Southwest 737 last week has brought renewed attention not only to the problem of aging planes, but also to problems in oversight of the airline industry.

In a report that received limited attention when it was released in December, the Transportation Department’s inspector general raised questions about the Federal Aviation Administration’s safety checks of airliners. According to the report, the agency had failed to perform on-time inspections of the major airlines in more than 300 instances [PDF] between fiscal years 2005 and 2009.

Its record was the worst with Southwest: "The Southwest Airlines inspection office missed the most inspections at the required time intervals,” the report said.

The FAA said in a statement at the time that it had made several changes to its inspection program and "is confident in its ability to oversee the National Aerospace System."

In 2008, the FAA faced criticism from investigators for acting too cozy with the airline industry. In particular, its relationship with Southwest had been described by the inspector general as an "overly collaborative relationship."

That conclusion came after two former FAA inspectors-turned-whistleblowers exposed a number of problems with the agency's oversight of Southwest. Among them: The agency had allowed Southwest to operate Boeing 737s that had not undergone mandatory inspections to detect cracks. Six of those planes were later found to have them, and the company settled with the FAA for $7.5 million.

A 2008 government report also found FAA oversight lagging as major airlines increasingly outsourced maintenance work to contractors in a drive to lower costs. 

Cracks in the fuselage, or the body of the plane, are believed to have caused Friday's emergency aboard Flight 812. The National Transportation Safety Board is still investigating but has said that the 15-year-old aircraft had "pre-existing fatigue" along the entire length of the tear. A former member of the NTSB told the Wall Street Journal that existing inspection procedures "weren't adequate to uncover" the problems.

The FAA is issuing an emergency directive today requiring airlines to conduct safety inspections on older models of the 737 after inspections over the weekend detected cracks on three more Southwest 737s. It has issued a number of directives over the years aimed at addressing concerns about cracks in aging Boeing 737s. Most of the U.S.-registered planes to which the latest directive applies are operated by Southwest.

Southwest has said that the particular cracks on Flight 812 are “a new and unknown issue." The company said the plane involved in Friday’s incident had undergone all required inspections. It also shifted the focus to Boeing: "This is a Boeing-designed airplane. This is a Boeing-produced airplane," a Southwest spokeswoman told the AP. "It's obviously concerning to us that we're finding skin-fatigue issues."

Boeing did not comment to the AP. Agence France Presse reported yesterday that Qantas, an Australian airline, is putting its aging Boeing 737s up for sale, intending to replace them with a newer model.

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