Purpose of the Study The Sept. 11, 2001, terrorist attacks on the United States have drawn public attention to the potential for a crash of a large modern aircraft into structures that are part of our nation’s critical infrastructure, including power plants. Aircraft impact issues were addressed in the licensing process for all 103 U.S. nuclear power reactors; however the evaluations were based on the premise that such a crash would be accidental. On this basis, the potential for aircraft impact is small, and has been evaluated using probabilistic assessment methods. The results of these evaluations indicate that for all but a few nuclear power plant sites—those located near major airports—the probability of a crash is low and a resulting requirement for aircraft impact evaluation was not included in the licensing by the U.S. Nuclear Regulatory Commission. Nonetheless, the nuclear power industry is confident that nuclear plant structures that house reactor fuel can withstand aircraft impacts, even though they were not specifically designed for such impacts. This confidence is predicated on the fact that nuclear plant structures have thick concrete walls with heavy reinforcing steel and are designed to withstand large earthquakes, extreme overpressures and hurricane force winds. The purpose of this study is to validate that confidence.