| 1 | MRS | Air Marshall Islands, Inc. | IATA: CW, Callsign: Marshall Islands, IATA Prefix: 778, Name changed from Airline of the Marshall Islands | MH | AVCODES |
| 2 | MRS | Airline of the Marshall Islands | IATA: CW, Callsign: Marshall Islands, IATA Prefix: 778, Name changed to Air Marshall Islands, Inc. | MH | AVCODES |
| 3 | MRS | Mars Avia CJSC | Callsign: Mars Cargo, | AM | AVCODES |
| 4 | MRS | Manufacturers Ry. Co. | 10/1957-7/2005 | | NAKINA |
| 5 | MRS | Manufacturers Ry. Co. of St. Louis | 1/1941-7/1954 | | NAKINA |
| 6 | MRS | Manufacturers Ry. Co. | 8/1920-4/1938 | | NAKINA |
| 7 | MRS | Manufacturers Ry. Co. | Apr-38 | | NRHS |
| 8 | MRS | Manufacturers Ry. Co. of St. Louis | Jan-52 | | NRHS |
| 9 | MRS | Manufacturers Ry. Co. | 10/57-7/2000 | | NRHS |
| 10 | MRS | MANUFACTURERS RAILWAY COMPANY (ANHEUSER-BUSCH INC.) | | | PWRC |
| 11 | MRS | Manufacturers Railway (Anheuser-Busch) | | | RSRV |
| 12 | MRS | Military Railway Service | | I | TRAFFIC |
| 13 | MRSB | MAGALLAN RIOS, BERTHA ISABEL | | | SCAC4 |
| 14 | MRSC | Manufacturers Railway Co. | Real: MRS, Anheuser-Busch, St.Louis | USA | TRAFFIC |
| 15 | MRSD | MACDONALD, RICHARD STUDIO | | | SCAC4 |
| 16 | MRSE | MORSE, KELSEY TRUCKING | | | SCAC4 |
| 17 | MRSF | MARS FREIGHT LTD | | | SCAC4 |
| 18 | MRSG | MRS GRISSOM'S SALADS INC | | | SCAC4 |
| 19 | MRSH | MERCER SHIPPING INC | | | SCAC4 |
| 20 | MRSI | MR | | | SCAC4 |
| 21 | MRSL | MRS Logistica | | BR | TRAFFIC |
| 22 | MRSM | MILLER, R & S TRUCKING | | | SCAC4 |
| 23 | MRSP | MARS TRANSPORT INC | | | SCAC4 |
| 24 | MRSR | MOUNT RANIER SCENIC RAILROAD | | | PWRC |
| 25 | MRSR | MARSHA | | | SCAC4 |
| 26 | MRSR | Manufacturers Railway Company of St. Louis | Real: MRS | USA | TRAFFIC |
| 27 | MRSS | MORRIS LOGISTICS INC | | | SCAC4 |
| 28 | MRSS | MRS Logistica S.A. | | BR | TRAFFIC |
| 29 | MRST | MARASTOR TRUCKING | | | SCAC4 |
| 30 | MRSU | MAERSK A/S | | DK | BIC |
| 31 | MRSU | A P MOLLER | | | SCAC4 |
| 32 | MRSV | MARITIME SERVICES LTD | | | SCAC4 |
| 33 | MRSX | Mile-High Railcar Services, Inc. | added 1/1988; eliminated 4/1993; 1/1994-7/2005 (not listed) | | NAKINA |
| 34 | MRSX | Mile-High Railcar Leasing, Inc. | added 10/1983; eliminated 1/1988 | | NAKINA |
| 35 | MRSX | Mile-High Railcar Leasing, Inc. | added 10/83; eliminated 1/88 | | NRHS |
| 36 | MRSX | Mile-High Railcar Services, Inc. | added 1/88; eliminated 4/93; 1/94-7/2000 | | NRHS |
| 37 | MRSX | *MILITARY OCEAN TERMINAL RAILROAD AT SUNNY POINT | | | PWRC |
| 38 | MRSX | +MILE-HIGH RAILCAR SERVICES, INC. | | | PWRC |
| 39 | MRSX | Mile-High Railcar Services | | | RSRV |
| 40 | MRSX | MILE-HIGH RAILCAR SERVICES, INC. | | | SCAC4 |
| 41 | MRSZ | MIDWEST RAIL SWITCHING SERVICES | | | PWRC |
