| 9701 | TTGX | Trailer Train Co. | 4/1970; added 1/1977 | | NAKINA |
| 9702 | TTGX | Trailer Train Co./TTX Co. (flat cars equipped with fully enclosed bi-level auto racks furnished by participant railroads) | 1/1980-1/1994 | | NAKINA |
| 9703 | TTGX | TTX Co. (flat cars equipped with fully enclosed bi-level auto racks furnished by participant railroads, equipped with end of car cush.) | 7/2000 | | NAKINA |
| 9704 | TTGX | Trailer Train Co. | Apr-70 | | NRHS |
| 9705 | TTGX | Trailer Train Co. (no definition) | Jan-75 | | NRHS |
| 9706 | TTGX | Trailer Train Co. | 4/70; added 1/77 | | NRHS |
| 9707 | TTGX | Trailer Train Co. (flat cars equipped with fully enclosed bi-level auto racks furnished by participant railroads) | 1/80; eliminated 1/92 | | NRHS |
| 9708 | TTGX | TTX Co. (flat cars equipped with fully enclosed bi-level auto racks furnished by participant railroads) | added 1/92; 1/94 | | NRHS |
| 9709 | TTGX | TTX Co. (flat cars equipped with fully enclosed bi-level auto racks furnished by participant railroads, equipped with end of car cush.) | Jul-00 | | NRHS |
| 9710 | TTGX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 9711 | TTGX | Trailer Train (TTX Corporation) | | | RSRV |
| 9712 | TTGX | TTX COMPANY | | | SCAC4 |
| 9713 | TTGY | TUFF TRANSPORT INC | | | SCAC4 |
| 9714 | TTH | Tarhan Tower Airlines | Founded in 2006. Ceased operations in Decemeber 2007. | TR | AVCODES |
| 9715 | TTH | Tarhan Tower Airlines | | | ICAO1 |
| 9716 | TTHB | TRUST TRUCKING | | | SCAC4 |
| 9717 | TTHC | TRANSPORT SERGE THIBERT INC | | | SCAC4 |
| 9718 | TTHE | THREE (3) T'S LTD | | | SCAC4 |
| 9719 | TTHH | TAYLORS TOWING & HEAVY HAULING LLC | | | SCAC4 |
| 9720 | TTHI | TRANSPORT HRL INC | | | SCAC4 |
| 9721 | TTHL | TRANSPORT THOM LTEE | | | SCAC4 |
| 9722 | TTHM | TRANSPORT HM | | | SCAC4 |
| 9723 | TTHN | TSD TRANSPORATION LP (DIVISION INTE | | | SCAC4 |
| 9724 | TTHU | TRANSPORTTECHNIK | | | SCAC4 |
| 9725 | TTHX | Trailer Train Co. | added 10/1966; 10/1966-1/1980; eliminated 1/1992 | | NAKINA |
| 9726 | TTHX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 9727 | TTHX | Trailer Train Co. (heavy duty chain equipped cars) | added 10/1966; 10/1966 | | NAKINA |
| 9728 | TTHX | Trailer Train Co. (FMS flats specifically equipped with heavy duty chains anchored to removable stake pocket castings — when tiedowns are removed car becomes same as MTTX) | 10/1968 | | NAKINA |
| 9729 | TTHX | Trailer Train Co. (flat cars, equipped with heavy duty chains anchored to removable stake pocket castings. When tie-downs are removed, car becomes same as 60' car stencilled ""MTTX"") | 4/1970-1/1980 | | NAKINA |
| 9730 | TTHX | Trailer Train Co./TTX Co. (flat cars equipped with 18 heavy-duty chains anchored to removable stake pocket castings. When tie-downs are removed, car becomes same as 60' flat cars stencilled MTTX) | 7/1985-7/2000 | | NAKINA |
| 9731 | TTHX | Trailer Train Co. (heavy duty chain equipped cars) | added 10/66; 10/66 | | NRHS |
| 9732 | TTHX | Trailer Train Co. (FMS flats specifically equipped with heavy duty chains anchored to removable stake pocket castings -- when tiedowns are removed car becomes same as MTTX) | Oct-68 | | NRHS |
| 9733 | TTHX | Trailer Train Co. | Apr-70 | | NRHS |
| 9734 | TTHX | Trailer Train Co. (flat cars, equipped with heavy duty chains anchored to removable stake pocket castings. When tie-downs are removed, car becomes same as 60' car stencilled "MTTX") | 1/75-1/80 | | NRHS |
| 9735 | TTHX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 9736 | TTHX | TTX Co. | added 1/92 | | NRHS |
| 9737 | TTHX | TTX Co. (flat cars equipped with 18 heavy-duty chains anchored to removable stake pocket castings. When tie-downs are removed, car becomes same as 60' flat cars stencilled MTTX) | 1/94-7/2000 | | NRHS |
| 9738 | TTHX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 9739 | TTHX | Trailer Train (TTX Corporation) | | | RSRV |
| 9740 | TTHX | TTX COMPANY | | | SCAC4 |
| 9741 | TTHY | TSI TRUCKING LLC | | | SCAC4 |
| 9742 | TTI | Aero Attie, S.A. de C.V. | Callsign: Aero Attie, | MEX | AVCODES |
| 9743 | TTI | TRANSKENTUCKY RAILROAD | | | PWRC |
| 9744 | TTI | Transkentucky Transportation | | USA | TRAFFIC |
| 9745 | TTIB | TOTAL TRANSPORT INC | | | SCAC4 |
| 9746 | TTIC | TRI-S TRUCKING, INC | | | SCAC1 |
| 9747 | TTIC | TRANSIT TEC INC | | | SCAC4 |
| 9748 | TTID | TUNDRA TRANSPORT INC | | | SCAC4 |
| 9749 | TTIE | TIGER TRANS INC | | | SCAC4 |
| 9750 | TTIK | TRANSPORTES INTERNACIONALES KARVI S | | | SCAC4 |
| 9751 | TTIL | TRANSPORTES INTERNACIONALES ZALDIVA | | | SCAC4 |
| 9752 | TTIM | T & T IMPORTS INC | | | SCAC4 |
| 9753 | TTIO | TRANSITION LLC | | | SCAC4 |
| 9754 | TTIP | TRAILER TRANSIT INC | | | SCAC4 |
| 9755 | TTIS | Transkentucky Transportation R.R. Co., Inc. | 1/1980; added 4/1980; eliminated 7/1980 | | NAKINA |
| 9756 | TTIS | Transkentucky Transportation Co., Inc. | 1/1980; added 7/1980; 1/1994; eliminated 7/1998; 7/2000-7/2005 | | NAKINA |
| 9757 | TTIS | Transkentucky Transportation R.R. Co., Inc. | 1/80; added 4/80; eliminated 7/80 | | NRHS |
| 9758 | TTIS | Transkentucky Transportation Co., Inc. | 1/80; added 7/80; 1/94; eliminated 7/98; 7/2000 | | NRHS |
| 9759 | TTIS | TRANSKENTUCKY TRANSPORTATION RAILROAD, INC. | | | PWRC |
| 9760 | TTIS | Transkentucky Transportation Railroad | | | RSRV |
| 9761 | TTIT | TIGER TOOL INTERNATIONAL INCORPORAT | | | SCAC4 |
| 9762 | TTIU | MASTERS GLOBAL LOGISTICS, INC. | | ROK | BIC |
| 9763 | TTIU | THAILAND TANTALUM INDUSTRY CORPORATION LTD | | | PWRC |
| 9764 | TTIU | Thailand Tantalum Industry Corporation Limited | | | RSRV |
| 9765 | TTIV | TUCSON TRANSPORT INC | | | SCAC4 |
| 9766 | TTIW | T T I INC | | | SCAC4 |
| 9767 | TTIX | Transcontinental Transport, Inc. | added 4/1956; 10/1957-4/1961; eliminated 4/1965 | | NAKINA |
| 9768 | TTIX | North American Car Corp. | added 4/1965; 7/1965-1/1980; eliminated 1/1984 | | NAKINA |
| 9769 | TTIX | General Electric Railcar Services Corp. | added 1/1984; eliminated 4/1989 | | NAKINA |
| 9770 | TTIX | TTX Co. | added 7/2007 | | NAKINA |
| 9771 | TTIX | TTX Co. (no definition) | added 7/2007 | | NAKINA |
| 9772 | TTIX | Transcontinental Transport, Inc. | 10/57-4/61; eliminated 4/65 | | NRHS |
| 9773 | TTIX | North American Car Corp. | added 4/65; 7/65-1/80 | | NRHS |
| 9774 | TTIX | General Electric Railcar Services Corp. | eliminated 4/89 | | NRHS |
| 9775 | TTIX | *(NATX) RETIRED 08-22-92 ATP [GEN. ELECTRIC RAILCAR SERVICE; NORTH AMERICAN CAR CORP.; TRANSCONTINENTAL TRANSPORT, INC.] | | | PWRC |
| 9776 | TTIX | *TRITON TRANSPORTATION, INC. | | | PWRC |
| 9777 | TTIX | +TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 9778 | TTIX | Trailer Train (TTX Corporation) | | | RSRV |
| 9779 | TTIX | TTX COMPANY | | | SCAC4 |
| 9780 | TTIY | TRANSPORTATION TECHNOLOGY INC | | | SCAC4 |
| 9781 | TTIZ | TANDEM TRANSPORT INCORPORATED | | | PWRC |
| 9782 | TTIZ | Tandem Transport | | | RSRV |
| 9783 | TTIZ | TANDEM TRANSPORT INC | | | SCAC4 |
| 9784 | TTJ | Tatra Jet, s.r.o. | Callsign: Tatra, | SK | AVCODES |
| 9785 | TTJA | TEMP TRANS LLC | | | SCAC4 |
| 9786 | TTJB | TRANSPORT J B | | | SCAC4 |
| 9787 | TTJC | TATLOCK, J & C & SON TRANSPORT LTD | | | SCAC4 |
| 9788 | TTJF | TSJ TRANSPORT INC | | | SCAC4 |
| 9789 | TTJJ | TIMBERLINE TRANSPORT INC | | | SCAC4 |
| 9790 | TTJK | TTD TRANSPORT | | | SCAC4 |
| 9791 | TTJL | TRIGUEROS TRUCKING | | | SCAC4 |
| 9792 | TTJM | TRANSPORTES AJM | | | SCAC4 |
| 9793 | TTJP | T & T TRANSPORTATION SERVICES LLC | | | SCAC4 |
| 9794 | TTJQ | TILLERY TRUCKING INC | | | SCAC4 |
| 9795 | TTJR | TOP TRUCKING CORP | | | SCAC4 |
| 9796 | TTJT | TRUAX, THOMAS JAMES, TRUCKING | | | SCAC1 |
| 9797 | TTJT | TRANSPORTES JESUS TORRES TORRES | | | SCAC4 |
| 9798 | TTJX | Trailer Train Co. | added 4/1970; 4/1970-1/1980; eliminated 1/1992 | | NAKINA |
| 9799 | TTJX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 9800 | TTJX | Trailer Train Co. (90-ton flat cars with special tie-down devices, fixtures and stake pockets) | added 4/1970; 4/1970 | | NAKINA |
