Soviet documents declassified in March 2003 showed that the KGB had conducted their own investigation of the accident, in addition to one government and two military investigations. The KGB's report dismissed various conspiracy theories, instead indicating that the actions of airbase personnel contributed to the crash. The report states that an air traffic controller provided Gagarin with outdated weather information, and that by the time of his flight, conditions had deteriorated significantly. Ground crew also left external fuel tanks attached to the aircraft. Gagarin's planned flight activities needed clear weather and no outboard tanks. The investigation concluded that Gagarin's aircraft entered a spin , either due to a bird strike or because of a sudden move to avoid another aircraft. Because of the out-of-date weather report, the crew believed their altitude to be higher than it actually was, and could not react properly to bring the MiG-15 out of its spin.