William Petterson MacCracken, Jr. (September 17, 1888 - September 1969) was a pioneer aviator. MacCracken became the first federal regulator of commercial aviation when then-Secretary of Commerce Herbert Hoover named him the first Assistant Secretary of Commerce for Aeronautics in 1926. During World War I he had served as a flight instructor, had served on the Chicago Aeronautical Commission, and was a member of the board of governors of the National Aeronautical Association when selected by Hoover.
After helping to draft key safety standards and regulations that became part of the 1930 Air Mail Act, MacCracken returned to his private law practice, where he continued to be involved in the growth of commercial aviation by representing many major airlines. For that reason Postmaster General Walter F. Brown asked him to preside over what was later scandalized as the Spoils Conference, to work out an agreement between the carriers and the Post office to consolidate air mail routes into transcontinental networks operated by the best-equipped and financially stable companies. This relationship left both exposed to charges of favoritism. When MacCracken refused later to testify before Congress, he was declared a lobbyist and found in contempt of Congress for allowing clients to rip up subpoenaed documents.
MacCracken filed a petition of habeas corpus in federal courts to overturn his arrest, but after litigation, the U.S. Supreme Court ruled that Congress had acted constitutionally, and denied the petition in the case Jurney v. MacCracken.