Edward Ruppelt claims that two U.S. Air Force Colonels requisitioned a twin engine B-25 bomber at Hamilton Field north of San Francisco for a cross-country flight to Colorado. At 3:40 P.M. MST while at 11,000 feet (3300 m) over the Carson Sink area east of Reno, according to Ruppelt, the two pilots saw three unknown aircraft make a left bank and fly quickly to within 400 to 800 yards (meters) of their B-25. The two men estimated the speed of the unknown aircraft to be at the very least three times that of the F-86. After four seconds, the aircraft sped away out of the vision of the pilots. When they landed in Colorado Springs, they contacted Air Defense Command Headquarters and learned that no civilian or military aircraft had been anywhere near the Carson Sink at the time of the incident. The two men dismissed the suggestion that they had seen F-86 jets, since they were intimately familiar with the design of that craft. Air Defense Command relayed the report to Ruppelt at Project Blue Book. In his subsequent book, The Report on Unidentified Flying Objects, Ruppelt characterized it as a "good UFO report with an unknown conclusion".