 Boom-equipped tankers have been obtained by several foreign countries as a result of USAF tanker procurement programs and U.S. foreign military sales.An estimated 63 boom-equipped tankers (KC-135, KC-10, A330 MRTT, KC-767, and KC-33) are operated by 14 foreign countries; in comparison, the USAF operates 457 KC-135 and KC-10 tankers.A boom operator must have a high school diploma or GED with 15 college credits.