| 1 | T&G | Tremont & Gulf Ry. (Co.) | 8/1920-4/1970 | | NAKINA |
| 2 | T&G | Tremont & Gulf Ry. | 4/38-4/70 | | NRHS |
| 3 | T&G | TREMONT & GULF RAILWAY CO. | | | PWRC |
| 4 | T&NO | Texas & New Orleans R.R. (Southern Pacific Lines in Texas and Louisiana) | 8/1920-7/1936 | | NAKINA |
| 5 | T&NO | Texas & New Orleans R.R. | 4/1938-4/1961 | | NAKINA |
| 6 | T&NO | Southern Pacific Co. (Texas and Louisiana Lines) | 7/1965 | | NAKINA |
| 7 | T&NO | Texas and New Orleans R.R. Co. (Southern Pacific Co.) | 10/1966 | | NAKINA |
| 8 | T&NO | Texas & New Orleans R.R. | 4/38-4/61 | | NRHS |
| 9 | T&NO | Southern Pacific Co. (Texas and Louisiana Lines) | Jul-65 | | NRHS |
| 10 | T&NO | Texas and New Orleans R.R. Co. (Southern Pacific Co.) | Oct-66 | | NRHS |
| 11 | T&NO | UNION PACIFIC RAILROAD [SOUTHERN PACIFIC TRANSP. CO.; TEXAS & NEW ORLEANS RR] | | | PWRC |
| 12 | T&P | Texas & Pacific Ry. | 8/1920-4/1970 | | NAKINA |
| 13 | T&P | Texas & Pacific Ry. | 4/38-4/70 | | NRHS |
| 14 | T&P | TEXAS & PACIFIC RY | | | PWRC |
| 15 | T&W | The Toledo and Western Ry. Co. | 8/1920-7/1932 | | NAKINA |
| 16 | T&W | TOLEDO & WESTERN RWY. CO. | | | PWRC |
| 17 | T-10 | FEDERAL RAILROAD OWNED VEHICLE | | | PWRC |
| 18 | T0 | Trans American Airlines, S.A. TACA Peru | ICAO: TPU, Callsign: Trans Peru, IATA Prefix: 530, Name changed to Avianca Peru. Established in 1999. Commenced operations in July 1999. | PE | AVCODES |
| 19 | T0 | Trans American Airlines, S.A. Avianca Peru | ICAO: TPU, Callsign: Trans Peru, IATA Prefix: 530, Ceased operations on 10 May 2020. Name changed from Trans American Airlines, S.A. TACA Peru. Established in 1999. Commenced operations in July 1999. | PE | AVCODES |
| 20 | T1 | Sysops, Inc. | Computer Reservations Systems (CRS) | USA | AVCODES |
| 21 | T1 | Tik Systems (Thailand) Co. Ltd. | Computer Reservations Systems (CRS) | T | AVCODES |
| 22 | T1 | Avtrasoft Limited | Computer Reservations Systems (CRS) | CY | AVCODES |
| 23 | T2 | Nakina Outpost Camp & Air Service Ltd. d/b/a Nakina Air Service | Designator T2* reinstated by IATA | CDN | AVCODES |
| 24 | T2 | Thai Air Cargo Co., Ltd. | ICAO: TCG, Callsign: Thai Cargo, IATA Prefix: 284, Designator T2 reinstated by IATA | T | AVCODES |
| 25 | T2 | Thai Air Cargo Co., Ltd. | ICAO: TCG, Callsign: Thai Cargo, IATA Prefix: 284, Designator T2 recalled by IATA | T | AVCODES |
| 26 | T2 | Tair Airways, Inc. | ICAO: TFB, | RP | AVCODES |
| 27 | T2 | Trans Mediterranean Airways S.A.L. | ICAO: TMA, Callsign: Tango Lima, IATA Prefix: 370, | RL | AVCODES |
| 28 | T2 | Fly Art Aviation | ICAO: FLB, Callsign: Rossignol, | TCH | AVCODES |
| 29 | T2 | TUM AeroCarga de Mexico, S.A. de C.V. | ICAO: MCS, Callsign: Carmex, IATA Prefix: 137, IATA designator changed from T8. Name changed from MCS AeroCarga de Mexico, S.A. de C.V. w.e.f. 01 August 2018. | MEX | AVCODES |
| 30 | T3 | Air Kilroe Limited t/a Eastern Airways | ICAO: EZE, Callsign: Eastflight, | GB | AVCODES |
| 31 | T3 | Air Kilroe Ltd. | ICAO: AKL, Callsign: Kilroe, Name changed to Eastern Airways Ltd. | GB | AVCODES |
| 32 | T3 | Transafricaine Air Cargo | ICAO: TCG, Callsign: Africargo, IATA Prefix: 728, Designator T3 recalled by IATA. | BF | AVCODES |
| 33 | T3 | Eastern Airways Limited | ICAO: EZE, Callsign: Eastflight, Formerly Air Kilroe Ltd. | GB | AVCODES |
| 34 | T3 | Air Kilroe Limited | ICAO: EZE, Callsign: Eastflight, | GB | AVCODES |
| 35 | T30 | Train Side View 30px | | | TRAFFIC |
| 36 | T4 | Hellas Jet S.A. | ICAO: HEJ, Callsign: Hellas Jet, IATA Designator changed to HJ. Subsidary of Cyprus Airways | GR | AVCODES |
| 37 | T4 | Rhoades Aviation, Inc. d/b/a transair | ICAO: RDS, Callsign: Rhoades Express, Operates transair Boeing 737 fleet. | USA | AVCODES |
| 38 | T4 | Transeast Airlines Ltd. | ICAO: TRL, Callsign: Lattrans, | LV | AVCODES |
| 39 | T4 | TRIP Linhas Aéreas | ICAO: TIB, Callsign: Trip, IATA designator changed to T4 | BR | AVCODES |
| 40 | T4 | TRIP Linhas Aéreas | ICAO: TIB, Callsign: Trip, IATA Prefix: 661, Founded in 1998. Merged in Azul Brazilian Airlines on 06 May 2014. IATA designator changed from T4* | BR | AVCODES |
| 41 | T4 | Topre Corporation | Computer Reservation System | J | AVCODES |
| 42 | T5 | Turkmenistan Airlines | ICAO: TUA, Callsign: Turkmenistan, IATA Prefix: 542, Designator T5 reinstated by IATA. ICAO designator changed from AKH | TM | AVCODES |
| 43 | T6 | Tavrey Aircompany | ICAO: TVR, Callsign: Tavrey, IATA Prefix: 204, | UA | AVCODES |
| 44 | T6 | 1Time Airline (Pty) Ltd | ICAO: RNX, Callsign: Next Time, Founded 2003. Commenced operations on 25 February 2004. Ceased operations on 02 November 2012. Name changed from Aeronexus Corporate Pty Ltd. | ZA | AVCODES |
| 45 | T6 | Twin Town Leasing Company | ICAO: TNY, Callsign: Twincal, IATA Prefix: 997, Name changed to Twin Air Calypso Limited, Inc. | USA | AVCODES |
| 46 | T6 | Twin Air Calypso Limited, Inc. | ICAO: TNY, Callsign: Twincal, IATA Prefix: 997, Ceased operations. Name changed from Twin Town Leasing Company | USA | AVCODES |
| 47 | T6 | Island Transvoyager, Inc. | ICAO: ITI, Callsign: Trans Voyager, Founded in 2002. Name changed to AirSWIFT Transport, Inc. ICAO designator changed to ATX. ICAO callsign changed to Airswift. w.e.f. October 2015. | RP | AVCODES |
| 48 | T6 | AirSWIFT Transport, Inc. | ICAO: ATX, Callsign: Airswift, Name changed from Island Transvoyager, Inc. ICAO Designator changed from ITI. ICAO Callsign changed from Trans Voyager. w.e.f. October 2015. | RP | AVCODES |
| 49 | T7 | Aircompany Trans Asian Airlines | ICAO: SRT, Callsign: Traser, Ceased operations during 1999. | KZ | AVCODES |
| 50 | T7 | Translift Airways Ltd. | ICAO: TLA, Callsign: Translift, Name changed to TransAer | IRL | AVCODES |
| 51 | T7 | Transcarga International Airways, C.A. | ICAO: TIW, Callsign: TIACA, IATA Prefix: 382, | YV | AVCODES |
| 52 | T7 | Twin Jet | ICAO: TJT, Callsign: Twinjet, IATA Prefix: 294, Established in May 2001. Commenced operations in October 2001. | F | AVCODES |
| 53 | T7 | TransGlobal Airways Corporation | ICAO: TCU, Callsign: Transglobal, Commenced operations in July 2005. | RP | AVCODES |
| 54 | T8 | Transportes Aereos Neuquen Sociedad Anonima | ICAO: NQN, Callsign: Taneu, Ceased operations. Name changed from Transportes Aereos Neuquen Sociedad del Estado | RA | AVCODES |
| 55 | T8 | Transportes Aereos Neuquen Sociedad del Estado | ICAO: NQN, Callsign: Taneu, Name changed to Transportes Aereos Neuquen Sociedad Anonima | RA | AVCODES |
| 56 | T8 | Worldwide Jet Charter LLC | ICAO: WWI, Callsign: Worldwide, Designator T8* recalled by IATA | USA | AVCODES |
| 57 | T8 | Telair International GmbH | Designator T8* recalled by IATA. Non-airline organisations relating to the airline industry. | D | AVCODES |
| 58 | T8 | MCS AeroCarga de Mexico, S.A. de C.V. | ICAO: MCS, Callsign: Carmex, IATA Prefix: 137, Name changed to TUM AeroCarga de Mexico, S.A. de C.V. w.e.f. 01 August 2018. | MEX | AVCODES |
| 59 | T8 | TUM AeroCarga de Mexico, S.A. de C.V. | ICAO: MCS, Callsign: Carmex, IATA Prefix: 137, IATA designator changed to T2*. Name changed from MCS AeroCarga de Mexico, S.A. de C.V. w.e.f. 01 August 2018. | MEX | AVCODES |
| 60 | T8 | CA Terra Avia S.r.l. | ICAO: TVR, Callsign: Terraavia, IATA Prefix: 357, | MD | AVCODES |
| 61 | T9 | Prime Air, Inc. d/b/a Transmeridian Airlines | ICAO: TRZ, Callsign: Trans-Meridian, Founded in 1995. Ceased operations on 29 September 2005. | USA | AVCODES |
| 62 | T9 | AB Varmlandsflyg | ICAO: SRL, Callsign: Starline, Name changed to Swedline Express AB w.e.f. 01 December 2002. | S | AVCODES |
| 63 | T9 | Aviator Aviation | ICAO: AVV, Callsign: Wing Man, Founded on 14 January 2015. | ET | AVCODES |
| 64 | T9 | Swedline Express AB | ICAO: SRL, Callsign: Starline, IATA designator changed to SM. Name changed from AB Varmlandsflyg w.e.f. 01 December 2002. | S | AVCODES |
| 65 | T9 | Thai Star Airlines | ICAO: TSX, Callsign: Thai Star, | T | AVCODES |
| 66 | T9 | Turpial Airlines, C.A. | ICAO: VTU, Callsign: Turpial, Commenced operations on 07 April 2017. | YV | AVCODES |
| 67 | TA | TACA International Airlines, S.A. | ICAO: TAI, Callsign: Taca, IATA Prefix: 202, Name changed to Avianca El Salvador on 21 May 2013. | ES | AVCODES |
| 68 | TA | Avianca El Salvador | ICAO: TAI, Callsign: Taca, IATA Prefix: 202, Name changed from TACA International Airlines, S.A. | ES | AVCODES |
| 69 | TA | Transafrican Air Limited | ICAO: TAK, Callsign: Transafrican, IATA Prefix: 400, | EAK | AVCODES |
| 70 | TA | Avianca Central America | ICAO: TAI, Callsign: Taca, IATA Prefix: 202, Name changed from Avianca El Salvador and previously TACA International Airlines, S.A. | ES | AVCODES |
| 71 | TA&G | Tennessee, Alabama & Georgia Ry. (Co.) | 7/1923-4/1970 | | NAKINA |
| 72 | TA&G | Tennessee, Alabama & Georgia Ry. Co. | 4/38-4/70 | | NRHS |
| 73 | TA&G | TENNESSEE, ALABAMA & GEORGIA RWY. CO. | | | PWRC |
| 74 | TA&W | Toledo, Angola & Western Ry. Co. | 4/1938-4/1970 | | NAKINA |
| 75 | TA&W | Toledo, Angola & Western Ry. Co. | 4/38-4/70 | | NRHS |
| 76 | TA&W | TOLEDO, ANGOLA & WESTERN RWY. CO. | | | PWRC |
| 77 | TAA | Aerotamatan, S.A. de C.V. | Callsign: Tamatan, | MEX | AVCODES |
| 78 | TAA | Aeroservicios de la Costa, S.A. de C.V. | Callsign: Aero Costa, | MEX | AVCODES |
| 79 | TAA | Aeroservicios de La Costa | | | ICAO1 |
| 80 | TAA | Trans Australia Arlines | Name is changed to Quantas in 1967 | AUS | TRAFFIC |
| 81 | TAAA | TRIPLE A DISTRIBUTION INC | | | SCAC3 |
| 82 | TAAA | TRANSPORTES ALTA SA DE CV | | | SCAC4 |
| 83 | TAAA | Aeroservicios de la Costa | Real: TAA | MEX | TRAFFIC |
| 84 | TAAB | TRANSPORTATION ASSOCIATES | | | SCAC3 |
| 85 | TAAB | TRANSATLANTIC SHIPPING AB | | | SCAC4 |
| 86 | TAAC | TITAN ARMORED CAR & COURIER INC | | | SCAC3 |
| 87 | TAAC | TRANSPORTES A T C M | | | SCAC4 |
| 88 | TAAD | TALBOT, A J & D M TRUCKING | | | SCAC3 |
| 89 | TAAD | TALBOT, A J & D M TRUCKING | | | SCAC4 |
| 90 | TAAE | TAALMAN ENGINEERED PRODUCTS | | | SCAC4 |
| 91 | TAAF | T-A-T MAR CORP | | | SCAC3 |
| 92 | TAAF | TRANSPORTES ANTONIO AMEZCUA FLORES | | | SCAC4 |
| 93 | TAAH | THOMPSON, AL TRUCKING INC | | | SCAC4 |
| 94 | TAAI | TIAN LAI TRANSPORTATION LTD | | | SCAC4 |
| 95 | TAAK | TRANSPORT AMERICA INC | | | SCAC3 |
| 96 | TAAL | TRANSALL INC | | | SCAC3 |
| 97 | TAAL | TRANSPORT ALAIN NADEAU INC | | | SCAC4 |
| 98 | TAAM | TARA MOTOR FREIGHT | | | SCAC3 |
| 99 | TAAN | TARA TRANSPORTATION | | | SCAC3 |
| 100 | TAAN | TARUS PRODUCTS INCORPORATED | | | SCAC4 |
