Hynek acted as scientific advisor to UFO studies undertaken by the U.S. Air Force under three consecutive projects: Project Sign (1947–1949), Project Grudge (1949–1952), and Project Blue Book (1952–1969).
A colaborat în calitate de consultant științific la studiile ufologice efectuate de către U.S. Air Force sub trei nume consecutive: Project Sign (1947–1949), Project Grudge (1949–1952) și Project Blue Book (1952 - 1969).