General Nathan Twining, who started Project Sign in 1947, was now Air Force Chief of Staff. In August 1954, he was to further codify the responsibilities of the 4602nd AISS by issuing an updated Air Force Regulation 200-2. In addition, UFOs (called "UFOBs") were defined as "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Investigation of UFOs was stated to be for the purposes of national security and to ascertain "technical aspects." AFR 200-2 again stated that Blue Book could discuss UFO cases with the media only if they were regarded as having a conventional explanation. If they were unidentified, the media was to be told only that the situation was being analyzed. Blue Book was also ordered to reduce the number of unidentified to a minimum.