Synopsis The Johns Hopkins University Applied Physics Laboratory, www.jhu.edu, was commissioned by the Air Transport Association (in concert with the FAA and the Aircraft Owners and Pilots Association) to determine the ability of GPS, GPS/WAAS and GPS/LAAS to satisfy Required Navigation Performance (RNP) "as expressed by accuracy, integrity, continuity and availability requirements." In other words, an assessment of the risks of using GPS, or GPS/WAAS, or GPS/LAAS, as a sole source of navigation information for flight. In brief, GPS alone won't hack it, although the other two might/will. Although the study dealt with the issue of intentional interference ("jamming") at some depth, it has been criticised for being somewhat cavalier about the consequences of a jamming incident onset while an aircraft is, say, on short final.
We include a PDF version of the full report, the Risk Assessment Study: Final Report