In 1941 Pan American Airways announced the first direct airmail service between Liberia (which was founded by freed American slaves) and the United States. To celebrate the inaugural flight, the Liberian Post Office overprinted existing stamps. Then, at the last minute, Pan Am postponed the flight until 1942.
unused example of surcharged airmail stamp; overprinted "First Flight / LIBERIA-U.S. / 1941 / 50c"
Museum ID: 2011.2005.7