| 2101 | USPZ | U.S. POSTAL SERVICE | | | PWRC |
| 2102 | USPZ | US Postal Service | | | RSRV |
| 2103 | USPZ | U S POSTAL SERVICE | | | SCAC4 |
| 2104 | USQA | USA TRANSPORT INC | | | SCAC4 |
| 2105 | USQI | US INLINE INC | | | SCAC4 |
| 2106 | USQN | UST INC | | | SCAC4 |
| 2107 | USQQ | U S COMEX | | | SCAC4 |
| 2108 | USQX | United States of America | 7/1930-7/1932 | | NAKINA |
| 2109 | USQX | United States of America (War Department, U.S.A.) | 7/1935 | | NAKINA |
| 2110 | USQX | Quartermaster Corps, War Department, U.S.A. | 7/1937-4/1938 | | NAKINA |
| 2111 | USQX | War Dept., U.S.A., Quartermaster Corps | 1/1941-1/1943 | | NAKINA |
| 2112 | USQX | War Dept., U.S.A., Office of the Chief of Transportation | 1/1945-4/1947 | | NAKINA |
| 2113 | USQX | Dept. of the Army, Office of the Chief of Transportation, Movement Division, Tank Car Section | 1/1950-1/1952 | | NAKINA |
| 2114 | USQX | Dept. of the Army | added 7/1953 | | NAKINA |
| 2115 | USQX | Dept. of the Army, Office of the Chief of Transportation, Railway Transport Service Division | 7/1954 | | NAKINA |
| 2116 | USQX | Department of the Army, Transportation Materiel Command, Marietta, Pennsylvania | eliminated 10/1955 | | NAKINA |
| 2117 | USQX | Department of the Army, Transportation Supply and Maintenance Command, St. Louis 1, Missouri | added 10/1955; eliminated 10/1956 | | NAKINA |
| 2118 | USQX | Quartermaster Corps, War Department, U.S.A. | Apr-38 | | NRHS |
| 2119 | USQX | Dept. of the Army, Office of the Chief of Transportation, Movement Division, Tank Car Section | Jan-52 | | NRHS |
| 2120 | USQX | U.S. DEPARTMENT OF DEFENSE - ARMY | | | PWRC |
| 2121 | USR | US Army Aeronautical Services Agency | Callsign: US Army, | USA | AVCODES |
| 2122 | USR | UTAH SOUTHERN RAILROAD COMPANY LLC | | | SCAC4 |
| 2123 | USR | Utah Southern Railway Co. | | USA | TRAFFIC |
| 2124 | USRA | URIBE SEGURA, ROSARIO | | | SCAC4 |
| 2125 | USRC | U S RUBBER RECLAIMING INC | | | SCAC4 |
| 2126 | USRD | U S ROAD FREIGHT EXPRESS INC | | | SCAC4 |
| 2127 | USRE | U S RACETRONICS | | | SCAC4 |
| 2128 | USRF | U S TRAFFIC INC | | | SCAC4 |
| 2129 | USRI | UNIVERSAL SERVICE RECYCLING INC | | | SCAC4 |
| 2130 | USRL | U S RAILWAYS INC | | | SCAC4 |
| 2131 | USRP | U S RAIL CORPORATION LLC | | | SCAC4 |
| 2132 | USRS | US RS, s.r.o. | | SK | VKM |
| 2133 | USRT | U S ART CO INC | | | SCAC4 |
| 2134 | USRV | U S TRANSPORT REPAIR & SERVICE INC | | | SCAC4 |
| 2135 | USRX | United States Rubber Co. | 7/1923-7/1937 | | NAKINA |
| 2136 | USRX | United States Rubber Products, Inc. | 4/1938 | | NAKINA |
| 2137 | USRX | United States Rubber Co. | 1/1941-10/1966; eliminated 7/1967 | | NAKINA |
| 2138 | USRX | Uniroyal, Inc. | added 7/1967; eliminated 4/1968 | | NAKINA |
| 2139 | USRX | U.S. Railcar, Inc. | 1/1994 (not listed) | | NAKINA |
| 2140 | USRX | US Railways Inc. | added 10/2003; eliminated 1/2004; 7/2005 (not listed) | | NAKINA |
| 2141 | USRX | United States Rubber Products, Inc. | Apr-38 | | NRHS |
| 2142 | USRX | United States Rubber Co. | 1/52-10/66; eliminated 7/67 | | NRHS |
| 2143 | USRX | Uniroyal, Inc. | added 7/67; eliminated 4/68 | | NRHS |
| 2144 | USRX | U.S. Railcar, Inc. | Jan-94 | | NRHS |
| 2145 | USRX | *UNIROYAL, INC. [UNITED STATES RUBBER CO.] | | | PWRC |
| 2146 | USRX | *U. S. ROAD & RAIL - MELVINDALE INC. | | | PWRC |
| 2147 | USRX | +U. S. RAILWAYS, INC. [U.S. RAILCAR, INC.] | | | PWRC |
| 2148 | USRX | US Railways | | | RSRV |
| 2149 | USRX | US RAILWAYS INC | | | SCAC4 |
| 2150 | USRZ | U. S. RECYCLING CO. | | | PWRC |
| 2151 | USS | Shuttle Inc. d/b/a USAir Shuttle | IATA: TB, Callsign: US Shuttle, Designator TB recalled by IATA | USA | AVCODES |
| 2152 | USS | Shuttle Inc. d/b/a USAir Shuttle | Callsign: US Shuttle, Designator TB recalled by IATA | USA | AVCODES |
| 2153 | USS | Unisped Spedition und Transportgesellschaft mbH | St. Ingbert (neu: Wincanton Rail) | D | privat-bahn.de |
| 2154 | USS | United states (of america) Navy | | USA | TRAFFIC |
| 2155 | USSA | U S SHIPPING INC | | | SCAC4 |
| 2156 | USSC | UNITED STATES STEEL CORP. | | | PWRC |
| 2157 | USSC | UNIVERSAL SCRAP SERVICE INC | | | SCAC4 |
| 2158 | USSE | UNITED SOLAR SYSTEMS DE MEXICO S A | | | SCAC4 |
| 2159 | USSH | USS HOLDING LLC | | | SCAC4 |
| 2160 | USSK | U.S. Steel Košice | | SK | VKM |
| 2161 | USSL | UNITED STATIONERS SUPPLY CO | | | SCAC4 |
| 2162 | USSR | ULISSE SRL | | | SCAC4 |
| 2163 | USST | UNITED STATES COLD STORAGE OF | | | SCAC4 |
| 2164 | USSU | UNITED STEEL & STRIP CORP. | | | PWRC |
| 2165 | USSU | United Steel and Strip Corporation | | | RSRV |
| 2166 | USSU | UNITED STEEL & STRIP CORP | | | SCAC4 |
| 2167 | USSV | UNITED SHIPPING SERVICES THREE INC | | | SCAC4 |
| 2168 | USSX | United States of America | 7/1923 | | NAKINA |
| 2169 | USSX | United States Sugar Corp. | 1/1943-4/1961; eliminated 1/1965 | | NAKINA |
| 2170 | USSX | United States Steel Corp. | added 10/1977; 1/1980; eliminated 7/1987 | | NAKINA |
| 2171 | USSX | Aristech Chemical Corp. | added 7/1987; eliminated 7/1988 | | NAKINA |
| 2172 | USSX | United States Steel Corp. | added 1/2004; eliminated 7/2004; 7/2005 (not listed) | | NAKINA |
| 2173 | USSX | United States Sugar Corp. | 1/52-4/61; eliminated 1/65 | | NRHS |
| 2174 | USSX | United States Steel Corp. | 1/80; eliminated 7/87 | | NRHS |
| 2175 | USSX | Aristech Chemical Corp. | added 7/87; eliminated 7/88 | | NRHS |
| 2176 | USSX | *UNITED STATES OF AMERICA | | | PWRC |
| 2177 | USSX | *UNITED STATES SUGAR CORP. | | | PWRC |
| 2178 | USSX | +U.S. STEEL CORP. (ARISTECH CHEMICAL CORP.) | | | PWRC |
| 2179 | USSX | United States Steel | | | RSRV |
| 2180 | USSX | UNITED STATES STEEL CORPORATION | | | SCAC4 |
| 2181 | USSX | U.S.Steel Co. | | USA | TRAFFIC |
| 2182 | USSY | U S SYNTEC CORP | | | SCAC4 |
| 2183 | USSZ | UNITED STATES SUGAR CO. | | | PWRC |
| 2184 | UST | Austro Aereo, S.A. | Callsign: Austro Aereo, | EC | AVCODES |
| 2185 | UST | Austro Aereo | | | ICAO1 |
| 2186 | UST | UNISPED Speditions- und Transportgesellschaft mbH | | DE | VKM |
| 2187 | USTB | U S TRANSPORT LLC | | | SCAC4 |
| 2188 | USTC | U. S. TRUCK COMPANY, INC | | | SCAC1 |
| 2189 | USTC | U S LOGISTICS INC | | | SCAC4 |
| 2190 | USTC | United States of America Transport Corps | | USA | TRAFFIC |
| 2191 | USTE | U S TRADING & LOGISTICS CORP | | | SCAC4 |
| 2192 | USTF | U S TRANSIT | | | SCAC4 |
| 2193 | USTG | UNITED STATES GOVERNMENT (FEDERAL RAILROAD ADMINISTRATION) | | | PWRC |
| 2194 | USTG | U S LOGISTICS INC | | | SCAC4 |
| 2195 | USTH | U S TRANSPORT INC | | | SCAC4 |
| 2196 | USTI | ULTRA SERVICE TRANSPORTATION INC | | | SCAC4 |
| 2197 | USTK | US STEADFAST TRUCKING LLC | | | SCAC4 |
| 2198 | USTM | USTRANSMEX S A DE C V | | | SCAC4 |
| 2199 | USTN | U S TRANSPORT FREIGHT SYSTEMS INC | | | SCAC4 |
| 2200 | USTO | U S TRAFFIC LIMITED | | | SCAC4 |
