On the morning of Tuesday, September 11, 2001, terrorists carried out a coordinated attack on the United States by hijacking four commercial jets. Two planes struck the World Trade Center towers in New York City, one hit the Pentagon, and a fourth, United Airlines Flight 93, crashed in a field near Shanksville, Pennsylvania after passengers, aware of the hijackers' intentions, planned to overthrow them. Recovery and rescue efforts continued for days and weeks as the scale of loss became clear, with the World Trade Center suffering the greatest number of injured and dead among its at least 50,000 daily occupants. A memorial by Reynaldo "Sonny" Rivera honors the three attack sites through bas-reliefs of Flight 93, the Pentagon, and the changed New York skyline marked by beams of light, and through sculptures of a police officer with a child, a firefighter, and three civilians that emphasize suffering, survival, humanity, courage, and the unity Americans found in the aftermath.