During the September 11 attacks, American Airlines Flight 11 flew near the Indian Point Energy Center en route to the World Trade Center. Mohamed Atta, one of the 9/11 hijackers/plotters, had considered nuclear facilities for targeting in a terrorist attack. Entergy says it is prepared for a terrorist attack, and asserts that a large airliner crash into the containment building would not cause reactor damage. Following 9/11 the NRC required operators of nuclear facilities in the U.S. to examine the effects of terrorist events and provide planned responses. In September 2006, the Indian Point Security Department successfully completed mock assault exercises required by the Nuclear Regulatory Commission. However, according to environmental group Riverkeeper, these NRC exercises are inadequate because they do not envision a sufficiently large group of attackers.