| 1 | GT | GB Airways Ltd. | ICAO: GBL, Callsign: GeeBee Airways, IATA Prefix: 171, Merged into Easyjet on 30 March, 2008. ICAO callsign changed from Gibair | GB | AVCODES |
| 2 | GT | Gibraltar Airways Ltd. | Callsign: Gibair, IATA Prefix: 171, Name changed to GB Airways Ltd. | GB | AVCODES |
| 3 | GT | GB Airways Ltd. | ICAO: GBL, Callsign: Gibair, IATA Prefix: 171, Name changed from Gibraltar Airways Ltd. | GB | AVCODES |
| 4 | GT | Vista Georgia Ltd. | ICAO: AJD, Callsign: Vista Georgia, Commenced operations on 05 August 2014. Ceased operations in May 2015. | GE | AVCODES |
| 5 | GT | P.C. Air Co., Ltd. | ICAO: PCA, Callsign: Piyo Air, Ceased operations. | T | AVCODES |
| 6 | GT | Air Guilin Co., Ltd. | ICAO: CGH, Callsign: Welkin, IATA Prefix: 730, Commenced operations on 25 June 2016. | PRC | AVCODES |
| 7 | GT | Grand Trunk Ry. | 4/1938-7/1954 | | NAKINA |
| 8 | GT | Grand Trunk Ry. (Canadian National Rys.) | 7/1930-7/1936 | | NAKINA |
| 9 | GT | Grand Trunk Ry. System (Canadian National Rys.) | 7/1923 | | NAKINA |
| 10 | GT | Grand Trunk Ry. | 4/38-1/52 | | NRHS |
| 11 | GT | CANADIAN NATIONAL [GRAND TRUNK RWY] | | | PWRC |
| 12 | GT | Grand Trunk Railway | | | RSRV |
| 13 | GT | GULF TRANSPORT COMPANY | | | SCAC4 |
| 14 | GT | Grand Trunk Ry. | | USA | TRAFFIC |
| 15 | GT&W | Gulf, Texas & Western Ry. Co. | 7/1923-7/1930 | | NAKINA |
| 16 | GT&W | GULF, TEXAS & WESTERN RWY. CO. | | | PWRC |
| 17 | GTA | GT Aviation | Callsign: GeeTee Avia, | GB | AVCODES |
| 18 | GTA | Gitanair | IATA: VG, Callsign: Gitanair, | I | AVCODES |
| 19 | GTA | City Airways Company Limited dba City Airways | IATA: E8, Callsign: City Airways, Commenced operations in September 2012. Suspended operations on 13 February 2016. | T | AVCODES |
| 20 | GTA | Grand Trunk Western R.R. Inc. | 1/1994-7/2005 | | NAKINA |
| 21 | GTA | Grand Trunk Western R.R. Co. | 1/1975-1/1980; eliminated 1/1983 | | NAKINA |
| 22 | GTA | Grand Trunk Western R.R. Co. | 1/75-1/80; eliminated 1/83 | | NRHS |
| 23 | GTA | Grand Trunk Western R.R. Inc. | 1/94-7/2000 | | NRHS |
| 24 | GTA | CANADIAN NATIONAL [GRAND TRUNK WESTERN] | | | PWRC |
| 25 | GTA | Grand Trunk Western (Canadian National Railway) | | | RSRV |
| 26 | GTAE | GTL ENTERPRISES INC | | | SCAC4 |
| 27 | GTAG | GABRIELS TOWING AND TRUCKING | | | SCAC4 |
| 28 | GTAH | GATES MANUFACTURING | | | SCAC4 |
| 29 | GTAL | GREAT AMERICAN LINES INC | | | SCAC4 |
| 30 | GTAN | GREAT TRANSPORTATION ENTERPRISE INC | | | SCAC4 |
| 31 | GTAO | GASEL TRANSPORTATION LINES INC | | | SCAC4 |
| 32 | GTAP | GANECA TRANSPORT (DIVISION OF TFI T | | | SCAC4 |
| 33 | GTAQ | GOGI TRUCKING INC | | | SCAC4 |
| 34 | GTAS | GUR-ISH TRUCKING LTD | | | SCAC4 |
| 35 | GTAT | GOGON TRANSPORT | | | SCAC4 |
| 36 | GTAU | GALLIKER TRANSPORT AG | | CH | BIC |
| 37 | GTAU | GALLIKER TRANSPORT AG | | | SCAC4 |
| 38 | GTAU | Greentrains | | AUS | TRAFFIC |
| 39 | GTAV | G T TRANSPORTATION SERVICES INC | | | SCAC4 |
| 40 | GTAW | GRANITE TOWN FARMS LTD | | | SCAC4 |
| 41 | GTAX | CHS Inc. | added 4/2007 | | NAKINA |
| 42 | GTAX | Cenex Harvest States Cooperatives | eliminated 4/2007 | | NAKINA |
| 43 | GTAX | Harvest States Cooperatives | added 1/1984; 1/1994-7/2000; eliminated 10/2000; 7/2005 (not listed) | | NAKINA |
| 44 | GTAX | Grain Terminal Association | added 7/1979; 1/1980; eliminated 1/1984 | | NAKINA |
| 45 | GTAX | Grain Terminal Association | added 7/79; 1/80 | | NRHS |
| 46 | GTAX | Harvest States Cooperatives | 1/94-7/2000; eliminated 10/2000 | | NRHS |
| 47 | GTAX | CHS, INC. [CENEX HARVEST STATES COOPERATIVES; GRAIN TERMINAL ASSOCIATION] | | | PWRC |
| 48 | GTAX | Harvest States Cooperative | | | RSRV |
| 49 | GTAX | CHS INC | | | SCAC4 |
| 50 | GTAX | Grain Terminal Association | | USA | TRAFFIC |
| 51 | GTB | Gleis- und Tiefbau AG | | CH | TRAFFIC |
| 52 | GTBA | GUITABEC INC | | | SCAC4 |
| 53 | GTBC | GAN-TRANS BROKERAGE LLC | | | SCAC4 |
| 54 | GTBE | GLS TRANSPORTATION INC | | | SCAC4 |
| 55 | GTBH | GROEN TRUCKING INC | | | SCAC4 |
| 56 | GTBI | GLOBAL TRANSPORT INC | | | SCAC4 |
| 57 | GTBJ | GARLYN TRUCKING LTD | | | SCAC4 |
| 58 | GTBK | GRT BROKERAGE | | | SCAC4 |
| 59 | GTBM | GRAEBEL TAMPA BAY MOVERS INC | | | SCAC4 |
| 60 | GTBO | G T BOLTON INC | | | SCAC4 |
| 61 | GTBP | GTB TRUCKING LTD | | | SCAC4 |
| 62 | GTBR | GREAT BEAR TRANSPORT LLC | | | SCAC4 |
| 63 | GTBS | GIESELMAN TRUCKING LLC | | | SCAC4 |
| 64 | GTBT | GWB TRUCKING | | | SCAC4 |
| 65 | GTBV | G & M TRANSPORTATION LLC | | | SCAC4 |
| 66 | GTBY | GST TRANSPORT SYSTEMS LP | | | SCAC4 |
| 67 | GTC | Golden International Airlines | Callsign: Golden Wings, 20 December 2005. Ceased opertions in 2007. | TR | AVCODES |
| 68 | GTC | Altin Havayolu Tasimaciligi Turizm Ve Ticaret | | | ICAO1 |
| 69 | GTC | Gulf Transport | 1/1975-1/1980 | | NAKINA |
| 70 | GTC | Gulf Transport | 1/75-1/80 | | NRHS |
| 71 | GTC | GULF TRANSPORT | | | PWRC |
| 72 | GTC | Gulf Transport | | | RSRV |
| 73 | GTCC | G & T TRUCKING INC | | | SCAC4 |
| 74 | GTCD | GOLD PRIORITY TRANSPORTATION | | | SCAC4 |
| 75 | GTCE | G T CARRIERS LTD | | | SCAC4 |
| 76 | GTCH | GREAT ALBERTA TRANSPORT LTD | | | SCAC4 |
| 77 | GTCI | GUSKI TRUCKING CO INC | | | SCAC4 |
| 78 | GTCK | GRAFF TRUCKING COMPANY, INC | | | SCAC1 |
| 79 | GTCL | GERMANY TANK CONTAINER LEASING GMBH | | | PWRC |
| 80 | GTCL | GENERAL TRANSPORT & CONSULTANTS INC | | | SCAC4 |
| 81 | GTCN | GROSA TRUCKING | | | SCAC4 |
| 82 | GTCR | GMT LOGISTICS LLC | | | SCAC4 |
| 83 | GTCS | GREAT CANADIAN STAMP COMPANY INC, T | | | SCAC4 |
| 84 | GTCU | GLOBAL TRADE CONTAINERS, LLC | | USA | BIC |
| 85 | GTCV | GUTIERREZ TRUCKING (MX-596227) | | | SCAC4 |
| 86 | GTCX | Westland Oil Co. | 1/1950 (not listed) | | NAKINA |
| 87 | GTCX | WESTLAND OIL CO. | | | PWRC |
| 88 | GTCX | GHOST TOWN & CAIRO | | | PWRC |
| 89 | GTDB | G & T DISTRIBUTION INC | | | SCAC4 |
| 90 | GTDD | GUELPH TOOL INC | | | SCAC4 |
| 91 | GTDG | G T D LOGISTICS INC | | | SCAC4 |
| 92 | GTDH | GOODNOW TRUCKING INC | | | SCAC4 |
| 93 | GTDL | GATR DLIVERY | | | SCAC4 |
| 94 | GTDM | GENUINE TRANSPORTATION INCORPORATED | | | SCAC4 |
| 95 | GTDN | GN TRUCKING | | | SCAC4 |
| 96 | GTDQ | GOOD TRANSPORT LLC | | | SCAC4 |
| 97 | GTDR | GRAND TRAVERSE DINNER TRAIN, THE | | | SCAC4 |
| 98 | GTDS | GTZ XPRESS INC | | | SCAC4 |
| 99 | GTDT | GARRETT, DON TRUCKING INC | | | SCAC4 |
| 100 | GTDV | GATLIN TRUCKING | | | SCAC4 |
