| 1 | TT | Air Lithuania | ICAO: KLA, Callsign: Kaunas, IATA Prefix: 843, | LT | AVCODES |
| 2 | TT | Texas International Airways, Inc. | Callsign: Texas, | USA | AVCODES |
| 3 | TT | Tiger Airways Australia Pty Ltd t/a Tigerair Australia | ICAO: TGG, Callsign: Tiggoz, Ceased operations on 25 March 2020. | AUS | AVCODES |
| 4 | TT | Braathens International Airways AB | ICAO: BIX, Callsign: Sun Trip, | S | AVCODES |
| 5 | TT | Toledo Terminal R.R. Co. | 8/1920-1/1980; eliminated 10/1984 | | NAKINA |
| 6 | TT | Toledo Terminal R.R. Co. | 4/38-1/80; eliminated 10/84 | | NRHS |
| 7 | TT | *TOLEDO TERMINAL RR | | | PWRC |
| 8 | TT | *TOONERVILLE TROLLEY | | | PWRC |
| 9 | TT | Toledo Terminal Railroad | | | RSRV |
| 10 | TT | TT modell railway | | TOY | TRAFFIC |
| 11 | TT | Trentino Trasporti | | IT | VKM |
| 12 | TTA | Transportes E Trabalho Aero | Name changed to TTA - Empresa Nacional de Transporte e Trabalho A�reo | MOC | AVCODES |
| 13 | TTA | TTA - Sociedade de Transporte e Trabalho Aereo | | | ICAO1 |
| 14 | TTAC | TRANSPORTES A C | | | SCAC4 |
| 15 | TTAD | TRANSPORTES ARANDAS | | | SCAC4 |
| 16 | TTAF | TICO TRANSPORT | | | SCAC4 |
| 17 | TTAG | T & T EVERGREEN | | | SCAC4 |
| 18 | TTAG | Trinidad & Tobago Air Guard | | TT | TRAFFIC |
| 19 | TTAH | TSP TRUCKING LLC | | | SCAC4 |
| 20 | TTAJ | TRANSPORTES ANDRES JIMENEZ | | | SCAC4 |
| 21 | TTAL | TRANSPORT ALAIN SIGOUIN | | | SCAC4 |
| 22 | TTAO | TRANSPORTES ARO | | | SCAC4 |
| 23 | TTAR | TRANSTAINER CORPORATION | | | SCAC1 |
| 24 | TTAR | TRACKDOWN TOWING & RECOVERY | | | SCAC4 |
| 25 | TTAT | T & T TRANSPORTS INC | | | SCAC4 |
| 26 | TTAU | TRET SRL | | I | BIC |
| 27 | TTAU | TRET SPA | | | SCAC4 |
| 28 | TTAX | Trailer Train Co. | added 4/1968; 10/1968-1/1980; eliminated 1/1992 | | NAKINA |
| 29 | TTAX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 30 | TTAX | Trailer Train Co. | added 4/1968 | | NAKINA |
| 31 | TTAX | Trailer Train Co. (89'4"" FC flats equipped with container adaptors, trailer hitches and bridge plates. Equipped with hydraulic draft gear) | 10/1968 | | NAKINA |
| 32 | TTAX | Trailer Train Co. (flush deck flat cars equipped with movable foldaway container pedestals, knock-down hitches and bridge plates; for transporting trailers or containers or combinations of both) | 4/1970 | | NAKINA |
| 33 | TTAX | Trailer Train Co. (flush deck flat cars equipped with foldaway container pedestals, knock-down hitches and bridge plates; for transporting trailers or containers or combinations of both) | 1/1975 | | NAKINA |
| 34 | TTAX | Trailer Train Co. (flush deck flat cars equipped with foldaway container pedestals, hitches and bridge plates; for transporting trailers or containers or combinations of both) | 1/1980-7/1985 | | NAKINA |
| 35 | TTAX | Trailer Train Co./TTX Co. (skeletonized, 5-unit, articulated all-purpose car for use between lift-on/lift-off facilities only, capable of carrying various combinations of trailers and/or containers of various lengths and widths) | 10/1991-7/2000 | | NAKINA |
| 36 | TTAX | Trailer Train Co. | added 4/68 | | NRHS |
| 37 | TTAX | Trailer Train Co. (89'4" FC flats equipped with container adaptors, trailer hitches and bridge plates. Equipped with hydraulic draft gear) | Oct-68 | | NRHS |
| 38 | TTAX | Trailer Train Co. | Apr-70 | | NRHS |
| 39 | TTAX | Trailer Train Co. (flush deck flat cars equipped with foldaway container pedestals, knock-down hitches and bridge plates; for transporting trailers or containers or combinations of both) | Jan-75 | | NRHS |
| 40 | TTAX | Trailer Train Co. (flush deck flat cars equipped with foldaway container pedestals, hitches and bridge plates; for transporting trailers or containers or combinations of both) | Jan-80 | | NRHS |
| 41 | TTAX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 42 | TTAX | TTX Co. | added 1/92 | | NRHS |
| 43 | TTAX | TTX Co. (skeletonized, 5-unit, articulated all-purpose car for use between lift on/lift off facilities only, capable of carrying various combinations of trailers and/or containers of various lengths and widths) | 1/94-7/2000 | | NRHS |
| 44 | TTAX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 45 | TTAX | Trailer Train (TTX Corporation) | | | RSRV |
| 46 | TTAX | TTX COMPANY | | | SCAC4 |
| 47 | TTB | Aerolineas Turisticas Del Caribe, S.A. de C.V. | Callsign: Aero Turisticas, | MEX | AVCODES |
| 48 | TTB | Aerolineas Turisticas del Caribe | | | ICAO1 |
| 49 | TTBA | TOMKEN TRANSPORTATION (BROKERAGE DI | | | SCAC4 |
| 50 | TTBB | TRI-CONTINENTAL TRUCK BROKERAGE INC | | | SCAC4 |
| 51 | TTBE | TETI BAKERY INC | | | SCAC4 |
| 52 | TTBF | TEPA TRUCKING | | | SCAC4 |
| 53 | TTBG | TTT BROKERAGE LLC | | | SCAC4 |
| 54 | TTBH | TRANSPORTES TRR SA DE CV | | | SCAC4 |
| 55 | TTBI | TRANSPORT BOUTET INC | | | SCAC4 |
| 56 | TTBK | TRIPLE T TRUCK BROKERS INC | | | SCAC4 |
| 57 | TTBL | T T BAIT LIMITED | | | SCAC4 |
| 58 | TTBO | TRANSPORT TRANSBO INC | | | SCAC4 |
| 59 | TTBP | TRINIDAD AND TOBAGO PETROLEUM | | | SCAC1 |
| 60 | TTBR | TRANSPORTES BARRERA | | | SCAC4 |
| 61 | TTBS | TANNER TRUCKING & BIT SERVICE LTD | | | SCAC4 |
| 62 | TTBT | TEDS TRUCK BODY & TRAILER SERVICE I | | | SCAC4 |
| 63 | TTBU | EQUIPPED4U BV | | NL | BIC |
| 64 | TTBV | TC TRANSPORT INC | | | SCAC4 |
| 65 | TTBW | TOMITAS TRUCKING INC | | | SCAC4 |
| 66 | TTBX | Trailer Train Co. | added 4/1968; 10/1968-1/1980; eliminated 1/1992 | | NAKINA |
| 67 | TTBX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 68 | TTBX | Trailer Train Co. | added 4/1968 | | NAKINA |
| 69 | TTBX | Trailer Train Co. (89'3"" and over FA flats equipped with bi-level automobile carrying superstructures furnished by member railroads. Cars are not equipped with hitches and bridge plates. Equipped with hydraulic draft gear) | 10/1968 | | NAKINA |
| 70 | TTBX | Trailer Train Co. (flat cars, length 89'4"" or over, equipped with bi-level auto racks furnished by member railroads) | 4/1970 | | NAKINA |
| 71 | TTBX | Trailer Train Co./TTX Co. (flat cars equipped with bi-level auto racks furnished by participant railroads) | 1/1975-7/2000 | | NAKINA |
| 72 | TTBX | Trailer Train Co. | added 4/68 | | NRHS |
| 73 | TTBX | Trailer Train Co. (89'3" and over FA flats equipped with bi-level automobile carrying superstructures furnished by member railroads. Cars are not equipped with hitches and bridge plates. Equipped with hydraulic draft gear) | Oct-68 | | NRHS |
| 74 | TTBX | Trailer Train Co. | Apr-70 | | NRHS |
| 75 | TTBX | Trailer Train Co. (flat cars equipped with bi-level auto racks furnished by participant railroads) | 1/75-1/80; eliminated 1/92 | | NRHS |
| 76 | TTBX | TTX Co. (flat cars equipped with bi-level auto racks furnished by participant railroads) | added 1/92; 1/94-7/2000 | | NRHS |
| 77 | TTBX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 78 | TTBX | Trailer Train (TTX Corporation) | | | RSRV |
| 79 | TTBX | TTX COMPANY | | | SCAC4 |
| 80 | TTC | Transteco | Callsign: Transteco, | ANG | AVCODES |
| 81 | TTC | Transteco | | | ICAO1 |
| 82 | TTC | AAR-TRANSPORTATION TEST CENTER | | | PWRC |
| 83 | TTC | The Train Company (RailInsight B.V.) | | NL | TRAFFIC |
| 84 | TTC | The Train Company | | NL | VKM |
| 85 | TTCC | TERMINAL TRUCKING COMPANY, INC | | | SCAC1 |
| 86 | TTCF | TOTAL TRANSPORTATION CONCEPT INC | | | SCAC4 |
| 87 | TTCG | TRANSPORTES DE CARGA GERSHEL S A DE | | | SCAC4 |
| 88 | TTCI | TRANSPORTES CISNEROS | | | SCAC4 |
| 89 | TTCM | TRANSPORT TRICAM INC | | | SCAC4 |
| 90 | TTCM | The Transport Company (Milwaukee) | City: Milwaukee | USA | TRAFFIC |
| 91 | TTCNG | T.T. CARGO mednarodni prevozi d.o.o. | | SI | VKM |
| 92 | TTCQ | TREAT CORE SUPPLY | | | SCAC4 |
| 93 | TTCS | TRANTEC SYSTEMS INC | | | SCAC4 |
| 94 | TTCU | TNC CHEMICALS CO. | | | PWRC |
| 95 | TTCU | TNC Chemicals | | | RSRV |
| 96 | TTCV | T & T CARGO SERVICES INC | | | SCAC4 |
| 97 | TTCW | TRIMAC TRANSPORTATION CENTRAL INC | | | SCAC4 |
| 98 | TTCX | Texas Chemical Co. | 8/1920-7/1935 | | NAKINA |
| 99 | TTCX | Consolidated Chemical Industries Inc. | 7/1937-4/1938 | | NAKINA |
| 100 | TTCX | Tulsa Tank Car Corp. | 1/1945 | | NAKINA |
