| 1 | MTR | Metroflight, Inc. | Callsign: Metro, | USA | AVCODES |
| 2 | MTR | Metroflight | | | ICAO1 |
| 3 | MTR | Youngstown & Southern Ry. Co. | 1/1994-7/2005 | | NAKINA |
| 4 | MTR | The Pittsburgh & Lake Erie R.R. Co. | eliminated 1/1993 | | NAKINA |
| 5 | MTR | Montour R.R. Co. | 4/1961-10/1966 & 1/1975-1/1980; eliminated 10/1986 | | NAKINA |
| 6 | MTR | Midland Terminal Ry. Co. | 8/1920-4/1947 | | NAKINA |
| 7 | MTR | Midland Terminal Rwy. Co. | Apr-38 | | NRHS |
| 8 | MTR | Montour R.R. Co. | 4/61-10/66 & 1/75-1/80; eliminated 10/86 | | NRHS |
| 9 | MTR | The Pittsburgh & Lake Erie R.R. Co. | eliminated 1/93 | | NRHS |
| 10 | MTR | Youngstown & Southern Ry. Co. | 1/94-7/2000 | | NRHS |
| 11 | MTR | *MIDLAND TERMINAL RWY. CO. | | | PWRC |
| 12 | MTR | *(PLW) PITTSBURG & LAKE ERIE RAILROAD [MONTOUR RAILROAD] | | | PWRC |
| 13 | MTR | +YOUNGSTOWN AND SOUTHERN RAILWAY | | | PWRC |
| 14 | MTR | Montour Railroad (Youngstown and Southern Railway) | | | RSRV |
| 15 | MTR | Mass Transit Railway | | HK | TRAFFIC |
| 16 | MTR | METRANS Rail s.r.o. | | CZ | VKM |
| 17 | MTRAM | M>Tram | Real: M>TRAM, City: Melbourne, The company was bought by Yarra Trams, Yarra Trams operates now the whole tramway network of Melbourne. | CDN | TRAFFIC |
| 18 | MTRC | METRO CARTAGE LLC | | | SCAC4 |
| 19 | MTRC | Montreal Transit Commission | | CDN | TRAFFIC |
| 20 | MTRD | MATEER OIL INC | | | SCAC4 |
| 21 | MTRD | METRANS Rail (Deutchland) GmbH | | DE | VKM |
| 22 | MTRG | MOTOR CARGO | | | SCAC1 |
| 23 | MTRH | MULTI-TRANS SHIPPING AGENCY INC | | | SCAC4 |
| 24 | MTRK | METROPOLITAN TRUCKING INC | | | SCAC4 |
| 25 | MTRL | MATERIALES ARJAMEX SA | | | SCAC4 |
| 26 | MTRM | METROPOLITAN MESSENGER SERVICE LLC | | | SCAC4 |
| 27 | MTRO | METROLINER INC | | | SCAC4 |
| 28 | MTRQ | MONTEREY MUSHROOMS INC | | | SCAC4 |
| 29 | MTRR | MILLER TRANSFER AND RIGGING CO | | | SCAC1 |
| 30 | MTRR | MILLER TRANSFER AND RIGGING CO | | | SCAC4 |
| 31 | MTRR | Montour Railroad | Real: M | USA | TRAFFIC |
| 32 | MTRS | MTR Shenzhen | Real: MTR, City: Shenzhen | PRC | TRAFFIC |
| 33 | MTRU | TRITON CONTAINER INTERNATIONAL LTD | | BM | BIC |
| 34 | MTRU | TAL International | | | RSRV |
| 35 | MTRU | MARTEC INTERNATIONAL | | | SCAC4 |
| 36 | MTRV | MEDINA TORRES SA DE CV | | | SCAC4 |
| 37 | MTRW | MARTIN DEL CAMPO BRINGAS, LUZ MARIA | | | SCAC4 |
| 38 | MTRX | TransMatrix, Inc. | added 10/1992; 1/1994-7/2000; eliminated 1/2004; 7/2005 (not listed) | | NAKINA |
| 39 | MTRX | TransMatrix, Inc. | added 10/92; 1/94-7/2000 | | NRHS |
| 40 | MTRX | (TMIX) TRANSMATRIX, INC. | | | PWRC |
| 41 | MTRX | TransMatrix | | | RSRV |
| 42 | MTRX | TRANSMATRIX, INC. | | | SCAC4 |
| 43 | MTRY | MOUNT TRAILER COMPANY | | | SCAC4 |
