| 1 | GTP | Aerotaxi Grupo Tampico, S.A. de C.V. | Callsign: Grupotampico, | MEX | AVCODES |
| 2 | GTP | Aerotaxi Grupo Tampico | | | ICAO1 |
| 3 | GTP | Grand Trunk Pacific Ry. (Canadian National Railways) | 7/1935-7/1954 | | NAKINA |
| 4 | GTP | Grand Trunk Pacific Ry. | 4/38-1/52 | | NRHS |
| 5 | GTP | CANADIAN NATIONAL RWYS. [GRAND TRUNK PACIFIC RAILWAY] (EXPIRED) | | | PWRC |
| 6 | GTP | Grand Trunk Pacific Railway | | | RSRV |
| 7 | GTPD | G & T SPECIALISTS INC | | | SCAC4 |
| 8 | GTPH | GRACE TRANSPORTATION INC | | | SCAC4 |
| 9 | GTPI | GRANT TRANSPORT INC | | | SCAC4 |
| 10 | GTPL | GO TRANSPORT LTD | | | SCAC4 |
| 11 | GTPLO | Gradski Transport Plovdiv | City: Plovdiv | BG | TRAFFIC |
| 12 | GTPO | GTP LOGISTICS | | | SCAC4 |
| 13 | GTPP | GLOBAL TANKER POOL PTE LTD | | | SCAC4 |
| 14 | GTPR | Grand Trunk Pacific Railway | | | RSRV |
| 15 | GTPS | GRAY TRANSPORT SERVICE LLC | | | SCAC4 |
| 16 | GTPT | GARRETT TRANSPORTATION SERVICES INC | | | SCAC4 |
| 17 | GTPU | GTS SPA | | I | BIC |
| 18 | GTPU | GTS SPA | | | SCAC4 |
| 19 | GTPV | GLOBAL TRANSPORTATION SYSTEMS INC | | | SCAC4 |
| 20 | GTPZ | TIT SERVICES | | | PWRC |
| 21 | GTPZ | TIT Services | | | RSRV |
| 22 | GTPZ | TIP SERVICES | | | SCAC4 |
