A while back, NASA surveyed 24,000 pilots about safety. The results were grim, with a much higher number of things like runway incursions, etc. than had been previously recorded, so NASA suppressed the survey because it “could materially affect the public confidence in, and the commercial welfare of, the air carriers and general aviation companies whose pilots participated in the survey.”

In other words, it would scare the hell out of people. Sorry, but covering the ass of the Airline industry should not be a reason for an official coverup, except of course when Bush and His Evil Minions^™ are in charge, I guess.