| 1 | TTX | Air Team A.S. | IATA: 8W, Callsign: Air Team, Designator 8W* recalled by IATA | N | AVCODES |
| 2 | TTX | Den Sivile Flyskole | Callsign: Sparrow, | N | AVCODES |
| 3 | TTX | Extraordin Air Aviation and Charter | Callsign: Twister, | USA | AVCODES |
| 4 | TTX | Thurber Tank Line Co. | 7/1930-7/1932 | | NAKINA |
| 5 | TTX | Texas Pacific Coal & Oil Co. | 7/1935-1/1946 | | NAKINA |
| 6 | TTX | Trailer Train Co. | added 4/1956; 10/1957-1/1980; eliminated 1/1992 | | NAKINA |
| 7 | TTX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 8 | TTX | Trailer Train Co. (not defined) | added 4/1956; 10/1957-4/1961 | | NAKINA |
| 9 | TTX | Trailer Train Co. (FC flat cars equipped with hitches, bridge plates and safety chains for the transportation of trailers) | 4/1963-7/1965 | | NAKINA |
| 10 | TTX | Trailer Train Co. (FC flat cars equipped with hitches and bridge plates for the transportation of trailers) | 10/1966-1/1980 | | NAKINA |
| 11 | TTX | Trailer Train Co./TTX Co. (flat cars equipped with collapsable hitches for the transportation of trailers) | 7/1985-7/2000 | | NAKINA |
| 12 | TTX | Texas Pacific Coal and Oil Co. | Apr-38 | | NRHS |
| 13 | TTX | Trailer Train Co. | 10/57-7/65 | | NRHS |
| 14 | TTX | Trailer Train Co. (FC flat cars equipped with hitches and bridge plates for the transportation of trailers) | 10/66-1/80 | | NRHS |
| 15 | TTX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 16 | TTX | TTX Co. | added 1/92 | | NRHS |
| 17 | TTX | TTX Co. (flat cars equipped with collapsable hitches for the transportation of trailers) | 1/94-7/2000 | | NRHS |
| 18 | TTX | *THURBER TANK LINE CO. | | | PWRC |
| 19 | TTX | *TEXAS PACIFIC COAL & OIL CO. | | | PWRC |
| 20 | TTX | +TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 21 | TTX | Trailer Train (TTX Corporation) | | | RSRV |
| 22 | TTX | TTX COMPANY | | | SCAC4 |
| 23 | TTX | | | USA | TRAFFIC |
| 24 | TTXA | TRANSPORT TRANS XLINE INC | | | SCAC4 |
| 25 | TTXD | TAMPA TRANSPORTATION & LOGISTICS LL | | | SCAC4 |
| 26 | TTXF | TM TRUCKING | | | SCAC4 |
| 27 | TTXH | THREE T TRUCKING LLC | | | SCAC4 |
| 28 | TTXJ | TRANSPLACE TEXAS LP (INTERMODAL FLE | | | SCAC4 |
| 29 | TTXK | TRANSPLACE TEXAS LP (LOWELL) | | | SCAC4 |
| 30 | TTXM | TRANSPLACE TEXAS, LP (DEDICATED FLE | | | SCAC4 |
| 31 | TTXO | TROY'S TRANSPORT INC | | | SCAC4 |
| 32 | TTXP | TORO TRANSPORT EXPRESS | | | SCAC4 |
| 33 | TTXR | TRANSCISCO TEXAN RAILWAY INC. | | | PWRC |
| 34 | TTXS | T & T EXPRESS INC | | | SCAC4 |
| 35 | TTXX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 36 | TTXX | TTX COMPANY | | | SCAC4 |
