The United States Transportation Department has found that nine major airlines in the United States outsourced over 70% of their major aircraft maintenance in 2007, compared to 34% in 2003.

A report from the inspector-general of the Transportation Department also found fault with the US Federal Aviation Administration (FAA) for having been slack in its supervision of repair facilities and for not closely tracking how much maintenance is farmed out and where it was performed.

The FAA requires each repair station to have a government inspection at least once a year. However, the Transportation Department’s report points out that “those inspections often are not being conducted by agency inspectors most familiar with standards and requirements of the airline whose planes are being repaired.”

The Federal Aviation Administration is the agency of the United States Transportation Department with authority to regulate and oversee all aspects of civil aviation in the United States. The FAA is the single most influential governmentally run aviation agency in the world, with the European Aviation Safety Agency coming a close second.

The nine US-based airlines examined by the Transportation Department were AirTran Airways, Alaska Airlines, America West Airlines, Continental Airlines, Delta Air Lines, JetBlue Airways, Northwest Airlines, Southwest Airlines, and United Airlines.

The FAA said in a statement that it agreed with the recommendations of the Transportation Department’s report. The report has recommended that the FAA should require airlines to provide more detailed information on the extent and location of outsourced repairs, ensure that carriers and repair stations are better able to spot and correct problems, and improve the documentation of inspection results.

The US Transportation Department’s investigators said in the report: “While steps have been taken to improve oversight, the FAA still faces challenges in determining where the most critical maintenance occurs and ensuring sufficient oversight. The FAA relies heavily on the airlines’ own oversight, but the airlines’ audit programmes were inefficient. In some cases, maintenance problems either went undetected or reoccurred.”

In one case, the investigators detected that that the FAA inspectors for a particular carrier only visited 4 of the carrier’s 15 outside contractors. In another, the FAA’s inspectors did not visit an airline’s foreign repair facility for as long as five years after it was initially approved by the FAA. And, by this time, the investigators found, “the facility had worked on 39 of the 53 engines that the airline had sent for maintenance.”

The report pointed out more lapses: in a number of repair stations, problems existed such as untrained mechanics, lack of required tools, and unsafe storage of aircraft parts. However, the investigators said a majority of the problems “were not immediate safety-of-flight issues, but they could “affect aircraft safety over time if left uncorrected.”

A few airlines – like American Airlines, the largest domestic carrier in the United States – conduct all maintenance in-house or within the United States, the report noted, but many carriers have increased the amount of work outsourced to foreign contractors.

According to the investigators, airlines, in their efforts to cut costs, continue to shift heavy airframe maintenance from in-house mechanics and engineers to hundreds of repair companies in the United States, Canada, Mexico and countries in Central America and Asia.

In 2007, the investigators found, 27% of heavy airframe maintenance was sent abroad – up from 21% in 2003.