two B-29 Superfortress observation planes had set out early in the morning with instructions from Oppenheimer to steer a course at least 15 miles west of the atomic detonation point, Trinity Site. Because of thunderstorms, the planes dropped from 23,000 to 18,000 feet before circling the Trinity Site during the first atomic bomb detonation. While "The Gadget" underwent field-testing at Trinity, the nuclear components for the bombs and the active materials were being sent piecemeal to Tinian. Shortly before the bomb testing at the Trinity site, components of Little Boy were driven from Los Alamos to Kirtland Field and then flown to San Francisco. This included some of the U-235. From San Francisco, they were transported to Hunters Point to board the cruiser , bound for Tinian. Following that, the Fat Man plutonium core and its initiator were driven down to Albuquerque. They left Kirtland Field on 26 July and were flown in a C-54 Skymaster to Tinian, where they arrived 28 July. Such was Kirtland Field's last important role in the U.S. defeat of Japan, thereby ending World War II. However, it was not its last connection with the Manhattan Project at Los Alamos, which largely would determine the base's fate in the postwar economy. To the east of the air base, at Oxnard Field, the U.S. Army also acquired 1,100 acres of land to develop a school for aircraft mechanics. An Air Depot Training Station, it was unofficially referred to as "Sandia Base". After various other incarnations—as a convalescent center and aircraft burial ground—Sandia Base became the precursor to Sandia National Laboratories when the Manhattan Project's Z Division relocated from Los Alamos to continue top-secret work development of atomic weapons. The New Mexico Proving Grounds (NMPG) was constructed concurrently with the development of the Albuquerque Army Air Base and the activities at the old Oxnard Field. It was built to the south to serve as the base for testing the top-secret proximity fuze, a device that played an important role in defeat of the German Vergeltungswaffe (V-1) rocket. The proximity fuze, a weapon that was later dubbed by the media as the second most important one developed during the war. By war's end, nearly 50,000 acres had been acquired for the NMPG, this acreage is to the south of the runway and main base that today makes up the greatest portion of Kirtland AFB. Postwar aircraft storage depot