 After cancellation of the XB-30 (a bomber version of the Constellation) in 1941, military officials gave Lockheed the go-ahead to build 80 Constellations (on the condition that other aircraft on their assembly lines would not be affected).With this, Lockheed could now put all attention towards building the Constellation airliner.On December 7, 1941, Japanese forces launched a surprise attack on the US Naval base in Pearl Harbor, Hawaii, causing the United States to enter the war.