| 1201 | UNPP | UNITED PACIFIC PET | | | SCAC4 |
| 1202 | UNPV | UNITED PALLET SERVICES INC | | | SCAC4 |
| 1203 | UNPX | Union Petroleum Co. | 8/1920-7/1923 | | NAKINA |
| 1204 | UNPX | Union Petroleum Co. (Sinclair Refining Co.) | 7/1930-7/1935 | | NAKINA |
| 1205 | UNPX | Sinclair Refining Co. | 7/1937-7/1954; eliminated 1/1958 | | NAKINA |
| 1206 | UNPX | Union Tank Car Co. | 10/1957; added 1/1958; 4/1961; added 7/1964; 7/1965-10/1966; added 1/1970; 4/1970; eliminated 1/1974 | | NAKINA |
| 1207 | UNPX | Procor Ltd. | added 1/1974; 1/1975-7/2005 | | NAKINA |
| 1208 | UNPX | Union Petroleum Co. (Sinclair Refining Co.) | Apr-38 | | NRHS |
| 1209 | UNPX | Sinclair Refining Co. | 1/52; eliminated 1/58 | | NRHS |
| 1210 | UNPX | Union Tank Car Co. | 10/57; added 1/58; 4/61; added 7/64; 7/65-10/66; added 1/70; 4/70; eliminated 1/74 | | NRHS |
| 1211 | UNPX | Procor Ltd. | added 1/74; 1/75-7/2000 | | NRHS |
| 1212 | UNPX | (PROX) PROCOR LIMITED [UNION TANK CAR CO.; SINCLAIR REFINING CO.; UNION PETROLEUM CO.] | | | PWRC |
| 1213 | UNPX | Union Petroleum (Procor) | | | RSRV |
| 1214 | UNPX | PROCOR LIMITED | | | SCAC4 |
| 1215 | UNPX | Procor Ltd. | | USA | TRAFFIC |
| 1216 | UNPY | UNITED PIPELINE SYSTEMS | | | SCAC4 |
| 1217 | UNQ | Unique Air Charter (Pty) Ltd | Callsign: Unique, | ZA | AVCODES |
| 1218 | UNQL | UNIQUE LOGISTICS INTERNATIONAL (H K | | | SCAC4 |
| 1219 | UNQP | UNIPAC SHIPPING INC LA PUENTE CA | | | SCAC4 |
| 1220 | UNQS | UNIQUE STORE FIXTURES LTD | | | SCAC4 |
| 1221 | UNR | Rivne Universal Avia | Callsign: Rivne Universal, Ceased operations | UA | AVCODES |
| 1222 | UNR | Rivne Universal Avia | | | ICAO1 |
| 1223 | UNRE | UNRAU ENTERPISES INC | | | SCAC4 |
| 1224 | UNRG | UNIVERSITY OF REGINA | | | SCAC4 |
| 1225 | UNRJ | UNRUH, J TRUCKING INC | | | SCAC4 |
| 1226 | UNRL | UNITED RENTALS OF CANADA INC | | | SCAC4 |
| 1227 | UNRR | UNIVERSAL REFUSE REMOVAL INC | | | SCAC4 |
| 1228 | UNRS | UNIVERSAL TRANSPORT INC | | | SCAC4 |
| 1229 | UNRT | UNION RIVER TRANSPORTATION INC | | | SCAC4 |
| 1230 | UNRU | UNITAS CONTAINERS LIMITED | | BM | BIC |
| 1231 | UNRZ | UNIVERSITY OF NORTH CAROLINA RAILROAD | | | PWRC |
| 1232 | UNS | Unsped Paket Servisi, Inc. | Callsign: Unsped, | TR | AVCODES |
| 1233 | UNS | Unsped Paket Servisi | | | ICAO1 |
| 1234 | UNSA | UNISTAR LINE | | | SCAC4 |
| 1235 | UNSC | UNISOURCE TRANSPORTATION SERVICES, INC | | | SCAC1 |
| 1236 | UNSC | UNIVERSITY OF CALGARY | | | SCAC4 |
| 1237 | UNSF | UNISHIPPERS | | | SCAC4 |
| 1238 | UNSG | UNISHIPPING | | | SCAC1 |
| 1239 | UNSG | UNISHIPPING MARITIME SERVICES | | | SCAC4 |
| 1240 | UNSH | UNISHIPPERS | | | SCAC4 |
| 1241 | UNSL | UNIVERSAL SHIPPING INC | | | SCAC4 |
| 1242 | UNSM | UNISHIPPERS | | | SCAC4 |
| 1243 | UNSP | UNIBULK SHIPPING ENTERPRISES S A | | | SCAC4 |
| 1244 | UNSQ | UNITED STEEL SERVICE INC | | | SCAC4 |
| 1245 | UNST | UNCLE STEVES TRUCKING LLC | | | SCAC4 |
| 1246 | UNSU | UNIOCEAN LINES | | GB | BIC |
| 1247 | UNSX | Unitrain Services (agent for Iowa Power and Light Co.) | added 10/1980; eliminated 4/1993 | | NAKINA |
| 1248 | UNSX | Midwest Power Systems | added 4/1993; 1/1994; eliminated 4/1996 | | NAKINA |
| 1249 | UNSX | MidAmerican Energy Co. | added 4/1996; 7/2000; eliminated 4/2003 | | NAKINA |
| 1250 | UNSX | JAIX Leasing Co. | added 4/2003; eliminated 1/2004 | | NAKINA |
| 1251 | UNSX | Railcar Custom Leasing, LLC | added 1/2004; eliminated 10/2004 | | NAKINA |
| 1252 | UNSX | Rail Logistics, LC | added 10/2004; 7/2005 | | NAKINA |
| 1253 | UNSX | Unitrain Services (agent for Iowa Power and Light Co.) | added 10/80; eliminated 4/93 | | NRHS |
| 1254 | UNSX | Midwest Power Systems | added 4/93; 1/94; eliminated 4/96 | | NRHS |
| 1255 | UNSX | MidAmerican Energy Co. | added 4/96; 7/2000 | | NRHS |
| 1256 | UNSX | *UNITRAIN SERVICES (AGENT FOR IOWA POWER & LIGHT) | | | PWRC |
| 1257 | UNSX | *MIDAMERICAN ENERGY COMPANY [(IOPRX) MIDWEST POWER SYSTEMS] | | | PWRC |
| 1258 | UNSX | +RAIL LOGISTICS, LC [RAILCAR CUSTOM LEASING, LLC; JAIX LEASING CO.] | | | PWRC |
| 1259 | UNSX | Unitrain Services | | | RSRV |
| 1260 | UNSX | RAIL LOGISTICS LC | | | SCAC4 |
| 1261 | UNT | Servicios Aereos Universitarios, S.A. de C.V. | Callsign: Universitario, | MEX | AVCODES |
| 1262 | UNT | Servicios Aereos Universitarios | | | ICAO1 |
| 1263 | UNTA | UNTAMED ART | | | SCAC4 |
| 1264 | UNTC | UNION TRANSFER AND STORAGE COMPANY | | | SCAC4 |
| 1265 | UNTH | UNITED TRANSPORT INC | | | SCAC4 |
| 1266 | UNTI | UNITEDTRANS LTD | | | SCAC4 |
| 1267 | UNTM | UNITED TRANSPORT CORP | | | SCAC4 |
| 1268 | UNTN | UNITRANS S A DE C V | | | SCAC4 |
| 1269 | UNTO | UNITED TRANSPORTATION LLC | | | SCAC4 |
| 1270 | UNTT | UNITEDSABINE LTD | | | SCAC4 |
| 1271 | UNTW | UNITED TRANSPORTATION INC, | | | SCAC4 |
| 1272 | UNTX | Unitrain, Inc. | added 10/1996; eliminated 4/1998 | | NAKINA |
| 1273 | UNTX | MRC Rail Services, LLC | added 4/1998; 7/2000; eliminated 10/2003 | | NAKINA |
| 1274 | UNTX | JAIX Leasing Co. | added 10/2003 | | NAKINA |
| 1275 | UNTX | Railcar Custom Leasing, LLC | 7/2005; eliminated 7/2007 | | NAKINA |
| 1276 | UNTX | Macquarie Rail Inc. | added 7/2007 | | NAKINA |
| 1277 | UNTX | Unitrain, Inc. | added 10/96; eliminated 4/98 | | NRHS |
| 1278 | UNTX | MRC Rail Services, LLC | added 4/98; 7/2000 | | NRHS |
| 1279 | UNTX | *RAILCAR CUSTOM LEASING, LLC [JAIX LEASING CO.; MRC RAIL SERVICES LLC; UNITRAIN, INC.] | | | PWRC |
| 1280 | UNTX | +MACQUARIE RAIL, INC. | | | PWRC |
| 1281 | UNTX | Unitrain (MRC Rail Services) | | | RSRV |
| 1282 | UNU | Unifly Servizi Aerei | Callsign: Unieuro, | I | AVCODES |
| 1283 | UNU | Unifly Servizi Aerei | | | ICAO1 |
| 1284 | UNUA | UNKNOWN US AIR CARRIER | | | SCAC1 |
| 1285 | UNUS | U-N-US TRUCKING INC | | | SCAC4 |
| 1286 | UNUU | UNISHIPPING | | | SCAC4 |
| 1287 | UNV | Ukraine Universal | Callsign: Ukraine Universal, Ceased operations. | UA | AVCODES |
| 1288 | UNVE | UNIVERSE COMPANY INC | | | SCAC4 |
| 1289 | UNVF | UNIVERSAL FABRICATING INC | | | SCAC4 |
| 1290 | UNVI | UNIVERSITY OF GUELPH | | | SCAC4 |
| 1291 | UNVL | UNIVERSAL FREIGHT LLC | | | SCAC4 |
| 1292 | UNVS | UNIQUE INVENTIONS INC | | | SCAC4 |
| 1293 | UNVV | UNIVERSITY OF VICTORIA, THE | | | SCAC4 |
| 1294 | UNVX | Universal Corp. | added 10/1960; 4/1961; eliminated 1/1963 | | NAKINA |
| 1295 | UNVX | Univar Canada Ltd. | added 4/2008 | | NAKINA |
| 1296 | UNVX | Universal Corp. | added 10/60; 4/61 | | NRHS |
| 1297 | UNVX | *UNIVERSAL CORP. | | | PWRC |
| 1298 | UNVX | +UNIVAR CANADA LTD. | | | PWRC |
| 1299 | UNVX | UNIVAR CANADA LTD | | | SCAC4 |
| 1300 | UNWL | UNIVERSITY OF WATERLOO | | | SCAC4 |
