The modern rank of general was established by the Officer Personnel Act of 1947, which authorized the President to designate certain positions of importance to carry that rank. Officers appointed to such positions bear temporary four-star rank while so serving, and are allowed to retire at that rank if their performance is judged satisfactory. The total number of active-duty four-star generals in the Air Force is limited to a fixed percentage of the number of Air Force general officers serving at all ranks.