In June 1946, the XB-35 made its first flight, a 45-minute trip from Hawthorne, California, to Muroc Dry Lake, without incident. The XB-35's engines and propellers were AAF property, and had not been tested for engine-propeller compatibility by either Pratt & Whitney, Hamilton Standard, or by the AAF which bought them at Wright Field without testing them or assuring reliability, and then shipped them to Northrop. Microfilmed records of reports and correspondence of the XB-35 program relate that after three or four flights, power plant and propeller vibrations increased, and the very efficient contra-rotating propellers began failing with frustrating frequency. Meetings were called by Northrop, of the AAF, Pratt & Whitney and Hamilton Standard where no one would take responsibility for correcting the AAF's engines and propellers. In addition, the AAF failed to supply the AC electrical alternator, insisting on Northrop using an onboard auxiliary power unit (APU) unit driven by an automotive engine which limited the high-altitude, high-speed XB-35 to test flights below . The AAF also refused to allow Northrop proposed modification of the bomb bays to carry the standard Mk. 3 atomic bomb, while at the same time declaring the AF would not buy the bomber unless it could carry the A-bomb. Northrop reluctantly agreed to try a single-rotation propeller, which slightly increased takeoff distance and a reduced rate-of-climb and maximum speed.