The second installment of Unfit for Flight, USA Today staff writer Thomas Frank's powerful series about the flawed investigations of general aviation accidents, calls into question the independence of the federal agency tasked with that immense job. Frank shows how the National Transportation Safety Board, swamped with work and often lacking technical expertise, depends on the aircraft manufacturers for many of its conclusions. Given the corporations' obvious self-interest, it shouldn't come as a surprise that the NTSB has overwhelmingly blamed the pilots, who are often unable to speak for themselves.

For me, the situation brought to mind the most noteworthy recent NTSB investigation in Minnesota. When the 35W bridge collapsed in Minneapolis in 2007, a consultant hired by the Minnesota Department of Transportation to do a parallel investigation and act as an expert witness for the state ended up providing crucial technical help to the NTSB. The agency's determination that a 40-year-old design flaw caused the collapse exonerated state officials, including its ambitious governor, Tim Pawlenty. I'm not the only one who's dubious about that conclusion, given the peculiar course of the NTSB probe and subsequent investigations that highlighted shortcomings in maintenance and inspections of the fracture-critical bridge.

Perhaps it's too much to expect one federal agency to possess all the expertise to investigate everything thrown its way, and the USA Today series rightly credits the NTSB with the astonishing modern safety record of commercial airline flights. Still, the fact that victims of defective aircraft have to go to court to find justice shows the gulf between the NTSB's lofty mission and what it actually does when small planes go down.

Above: File photo of NTSB workers on site with fragments of 35W bridge, 2008