Bockscar, sometimes called Bock's Car, is the name of the United States Army Air Forces B-29 bomber that dropped the Fat Man nuclear weapon over the Japanese city of Nagasaki in the second atomic bombing of World War II. One of 15 Silverplate B-29s used by the 509th, Bockscar was built at the Glenn L. Martin Aircraft Plant at Bellevue, Nebraska at what is now Offutt Air Force Base, and delivered to the United States Army Air Forces on 19 March 1945. It was assigned to the 393d Bombardment Squadron, 509th Composite Group to Wendover Army Air Field, Utah in April.