The report was considered highly flawed due to the survey methodology. The pilot survey was anonymous, so specific incidents could have been counted more than once.
See
http://technology.newscientist.com/c...ty-survey.html
Partial extract
The agency commissioned a telephone pollster to ask 29,000 pilots about their near misses, runway collisions and technical problems. At first, the poll seemed to show that these events had previously been alarmingly under-reported. Engine failures, for instance, were cited in NASA's survey at four times the rate recorded in the Federal Aviation Administration's incident records.
The problem is that NASA appears to have counted some incidents more than once. Pilots were given anonymity, so NASA can't tell when several reports of an incident refer to the same event. Explaining the gaffe to the House Committee on Science and Technology on 31 October, NASA chief Mike Griffin admitted the figures were "simply not credible".