| 1 | MTT | Mastair | Callsign: Blue Mast, | BIH | AVCODES |
| 2 | MTT | Orion S.p.A. | | I | AVCODES |
| 3 | MTTB | MULTI TRADE TERMINALS INC | | | SCAC4 |
| 4 | MTTC | MATTIC INDUSTRIES LIMITED | | | SCAC4 |
| 5 | MTTE | MARTIN TRUCKING 33 LLC | | | SCAC4 |
| 6 | MTTG | MITCHELL TRUCKING | | | SCAC4 |
| 7 | MTTH | MIDWEST TRANSPORT & TRUCKING INC | | | SCAC4 |
| 8 | MTTL | MT TRANSPORTATION AND LOGISTICS SER | | | SCAC4 |
| 9 | MTTM | MONTANA TRUCKING INC | | | SCAC4 |
| 10 | MTTO | MOTTO TRUSS INC | | | SCAC4 |
| 11 | MTTP | MTS TRANSPORTATION INC | | | SCAC4 |
| 12 | MTTQ | MACAO TAK TRANSPORT INC | | | SCAC4 |
| 13 | MTTS | MT TRANSPORTES Y SERVICIOS | | | SCAC4 |
| 14 | MTTU | Mariupol Tram-Trolleybus Administration | City: Mariupol | UA | TRAFFIC |
| 15 | MTTX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 16 | MTTX | Trailer Train Co. | added 10/1964; 7/1965-1/1980; eliminated 1/1992 | | NAKINA |
| 17 | MTTX | Trailer Train Co. | added 10/1964 | | NAKINA |
| 18 | MTTX | Trailer Train Co. (FM flat cars for general service) | 7/1965-10/1968 | | NAKINA |
| 19 | MTTX | Trailer Train Co. (60' flat cars with stake pockets and lading strap anchors for general service; or 85' flat cars with 16 stake pockets, 8 per side, for transporting long pipe) | 4/1970-7/1985 | | NAKINA |
| 20 | MTTX | Trailer Train Co./TTX Co. (60' flat cars with stake pockets for general service; or 85' flat cars with sixteen stake pockets, 8 per side, for transporting long pipe, also 89' cars installed with bulkheads) | 10/1991-1/1994 | | NAKINA |
| 21 | MTTX | TTX Co. (60' flat cars with stake pockets for general service; or 85' flat cars with sixteen stake pockets, 8 per side, for transporting long pipe, also 89' cars installed with bulkheads, equipped with end of car cush.) | 7/2000 | | NAKINA |
| 22 | MTTX | Trailer Train Co. | Jul-65 | | NRHS |
| 23 | MTTX | Trailer Train Co. (FM flat cars for general service) | 10/66-10/68 | | NRHS |
| 24 | MTTX | Trailer Train Co. | Apr-70 | | NRHS |
| 25 | MTTX | Trailer Train Co. (60' flat cars with stake pokcets and lading strap anchors for general service; or 85' flat cars with 16 stake pockets, 8 per side, for transporting long pipe) | 1/75-1/80 | | NRHS |
| 26 | MTTX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 27 | MTTX | TTX Co. | added 1/92 | | NRHS |
| 28 | MTTX | TTX Co. (60' flat cars with stake pockets for general service; or 85' flat cars with sixteen stake pockets, 8 per side, for transporting long pipe, also 89' cars installed with bulkheads) | Jan-94 | | NRHS |
| 29 | MTTX | TTX Co. (60' flat cars with stake pockets for general service; or 85' flat cars with sixteen stake pockets, 8 per side, for transporting long pipe, also 89' cars installed with bulkheads, equipped with end of car cush.) | Jul-00 | | NRHS |
| 30 | MTTX | TTX COMPANY | | | PWRC |
| 31 | MTTX | Trailer Train (TTX Corporation) | | | RSRV |
| 32 | MTTX | TTX COMPANY | | | SCAC4 |
| 33 | MTTZ | MT. TOM | | | PWRC |