| 5201 | HTT | Air Tchad | | | ICAO1 |
| 5202 | HTTA | HATTA ENTERPRISES LTD | | | SCAC4 |
| 5203 | HTTB | HIGH TOWER TRANSPORTATION BROKERAGE | | | SCAC4 |
| 5204 | HTTD | HIGH TECH TRANSPORTATION INC | | | SCAC4 |
| 5205 | HTTG | HALL, TREVOR TRUCKING | | | SCAC4 |
| 5206 | HTTH | HATTENHAUER DISTRIBUTING CO | | | SCAC4 |
| 5207 | HTTI | HEARTLAND TRANSPORTATION INC | | | SCAC4 |
| 5208 | HTTM | HAMMOND TRANSPORTATION INC | | | SCAC4 |
| 5209 | HTTN | HART TRUCKING INC | | | SCAC4 |
| 5210 | HTTP | HILL TOP TRUCKING | | | SCAC4 |
| 5211 | HTTQ | HI-TECH TRUCKING INC. | | | SCAC4 |
| 5212 | HTTS | HOUNDSTOOTH TRANSPORTATION INC | | | SCAC4 |
| 5213 | HTTT | HUNT TRANSPORT INC | | | SCAC4 |
| 5214 | HTTV | HANLEY, TIM TRUCKING LLC | | | SCAC4 |
| 5215 | HTTW | HITTSON TRANSPORT INC | | | SCAC4 |
| 5216 | HTTX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 5217 | HTTX | Trailer Train Co. | added 4/1968; 10/1968-1/1980; eliminated 1/1992 | | NAKINA |
| 5218 | HTTX | Trailer Train Co. | added 4/1968 | | NAKINA |
| 5219 | HTTX | Trailer Train Co. (FMS flats specifically equipped with heavy duty chains, snubbers and turnbuckles, secured to moveable and retractable tiedown anchors, in four longitudinal channels) | 10/1968 | | NAKINA |
| 5220 | HTTX | Trailer Train Co./TTX Co. (flat cars equipped with 38 heavy duty chains, with snubbers and turnbuckles, each secured to movable and retractable tie-down winches in 4 longitudinal channels, for transporting large earth moving equipment) | 4/1970-1/1994 | | NAKINA |
| 5221 | HTTX | TTX Co. (flat cars equipped with 38 heavy duty chains, with snubbers and turnbuckles, each secured to movable and retractable tie-down winches in 4 longitudinal channels, for transporting large earth-moving equipment, equipped with end of car cush.) | 7/2000 | | NAKINA |
| 5222 | HTTX | Trailer Train Co. | added 4/68 | | NRHS |
| 5223 | HTTX | Trailer Train Co. (FMS flats specifically equipped with heavy duty chains, snubbers and turnbuckles, secured to moveable and retractable tiedown anchors, in four longitudinal channels) | Oct-68 | | NRHS |
| 5224 | HTTX | Trailer Train Co. | Apr-70 | | NRHS |
| 5225 | HTTX | Trailer Train Co. (flat cars equipped with 38 heavy duty chains, with snubbers and turnbuckles, each secured to movable and retractable tie-down winches in 4 longitudinal channels, for transporting large earth moving equipment) | 1/75-1/80; eliminated 1/92 | | NRHS |
| 5226 | HTTX | TTX Co. (flat cars equipped with 38 heavy duty chains, with snubbers and turnbuckles, each secured to movable and retractable tie-down winches in 4 longitudinal channels, for transporting large earth moving equipment) | added 1/92; 1/94 | | NRHS |
| 5227 | HTTX | TTX Co. (flat cars equipped with 38 heavy duty chains, with snubbers and turnbuckles, each secured to movable and retractable tie-down winches in 4 longitudinal channels, for transporting large earth-moving equipment, equipped with end of car cush.) | Jul-00 | | NRHS |
| 5228 | HTTX | TTX COMPANY | | | PWRC |
| 5229 | HTTX | Trailer Train (TTX Corporation) | | | RSRV |
| 5230 | HTTX | TTX COMPANY | | | SCAC4 |
| 5231 | HTU | Yunnan Hong Tu Airlines Co., Ltd. | IATA: A6, Callsign: Hong Land, IATA Prefix: 389, Name changed to Air Travel Co., Ltd. ICAO Designator changed to OTC. | PRC | AVCODES |
| 5232 | HTUU | KIECA TRANS | | PL | BIC |
| 5233 | HTVN | HETCO VAN LINES INC | | | SCAC4 |
| 5234 | HTW | Hoosac Tunnel & Wilmington | 1/1994-7/2000 | | NAKINA |
| 5235 | HTW | Hoosac Tunnel & Wilmington | 1/94-7/2000 | | NRHS |
| 5236 | HTW | *HOOSAC TUNNEL AND WILMINGTON RAILROAD CO. | | | PWRC |
| 5237 | HTW | Hoosac Tunnel and Wilmington | | | RSRV |
| 5238 | HTWA | HODGE TRANSPORTATION & WAREHOUSING | | | SCAC4 |
| 5239 | HTWC | HALAL TOWING INC | | | SCAC4 |
| 5240 | HTWD | HOOSIER TRADEWINDS INC | | | SCAC4 |
| 5241 | HTWF | H2O FARMS | | | SCAC4 |
| 5242 | HTWG | HARTWIG, C TRANSPORT | | | SCAC4 |
| 5243 | HTWH | HAMILTON, E H TRUCKING & | | | SCAC4 |
| 5244 | HTWI | HARTWIG AIRCRAFT FUEL CELL REPAIR I | | | SCAC4 |
| 5245 | HTWJ | HTW LOGISTICS | | | SCAC4 |
| 5246 | HTWK | HAULMARK TRUCKING INC | | | SCAC4 |
| 5247 | HTWM | HATCHER, WILLIAM RAY TRUCKING CO | | | SCAC4 |
| 5248 | HTWQ | HAMNER TOWING INC | | | SCAC4 |
| 5249 | HTWT | HOT WATER TRUCKING LLC | | | SCAC4 |
| 5250 | HTWV | H TWO (2) | | | SCAC4 |
| 5251 | HTWY | HUTTER, WALLY OIL CO | | | SCAC4 |
| 5252 | HTX | Houston Tank Car Co. | 1/1952-10/1957; eliminated 4/1960 | | NAKINA |
| 5253 | HTX | The Hewitt Transportation Co. (The Hewitt Soap Co., Inc.) | 7/1937-4/1938 | | NAKINA |
| 5254 | HTX | The Hewitt Soap Co., Inc. | 7/1935 | | NAKINA |
| 5255 | HTX | The Hewitt Soap Co., Inc. | Apr-38 | | NRHS |
| 5256 | HTX | Houston Tank Car Co. | 1/52-10/57 | | NRHS |
| 5257 | HTX | HEWETT SOAP CO., INC. (HEWITT TRANSPORTATION CO.) | | | PWRC |
| 5258 | HTXC | HEAT TRANSFER LLC | | | SCAC4 |
| 5259 | HTXG | HIRTE TRANSFER & STORAGE | | | SCAC4 |
| 5260 | HTXI | HOPE TRANSPORT INC | | | SCAC4 |
| 5261 | HTXL | HIALEAH TRANSPORT LLC | | | SCAC4 |
| 5262 | HTXN | HEARNE TRANSPORTATION | | | SCAC4 |
| 5263 | HTXO | HAT TRANSPORT LLC | | | SCAC4 |
| 5264 | HTXT | HOLBORN TRANSPORT | | | SCAC4 |
| 5265 | HTXU | JINGMEN HONGTU SPECIAL AIRCRAFT MANUFACTURING CO LTD | | PRC | BIC |
| 5266 | HTY | Global Aeronautics Solutions Corp, S.L. t/a HELITY Copter Airlines | Callsign: Helity, | E | AVCODES |
| 5267 | HTYI | HARTLEY TRANSPORTATION INC | | | SCAC4 |
| 5268 | HTZI | HEITZ TRUCKING, INC | | | SCAC1 |
| 5269 | HTZI | HEITZ TRUCKING INC | | | SCAC4 |
| 5270 | HTZL | HETZELS OVERLAND TRANSPORT INC | | | SCAC4 |
| 5271 | HTZS | HOTZ ENVIRONMENTAL SERVICES INC | | | SCAC4 |
| 5272 | HU | Hainan Airlines Company Limited | ICAO: CHH, Callsign: Hainan, IATA Prefix: 880, Name changed to Hainan Airlines Holding Company Limited. IATA designator changed from HX | PRC | AVCODES |
| 5273 | HU | Formosa Airlines Corp. | ICAO: FOS, Designator HU recalled by IATA. Formerly Yung Shing Airlines | RC | AVCODES |
| 5274 | HU | Central Airlines (Nigeria) Limited. | ICAO: SEN, Callsign: Hotel Uniform, | WAN | AVCODES |
| 5275 | HU | Hainan Airlines Holding Company Limited | ICAO: CHH, Callsign: Hainan, IATA Prefix: 880, Name changed from Hainan Airlines Company Limited. IATA designator changed from HX | PRC | AVCODES |
| 5276 | HU | HUPAC SpA | | IT | VKM |
| 5277 | HUA | Humber Aviation Ltd. | Callsign: Humber Air, | GB | AVCODES |
| 5278 | HUAC | HUDSON ARMORED CAR & | | | SCAC4 |
| 5279 | HUAF | HUA FENG (USA) LOGISTICS INC | | | SCAC4 |
| 5280 | HUAF | Hungarian Air Force | Real: HUF | H | TRAFFIC |
| 5281 | HUAI | HUNDER, MYLES | | | SCAC4 |
| 5282 | HUAL | HUB AIRLINES INC | | | SCAC4 |
| 5283 | HUAN | HUB CITY ATLANTA TERMINALS INC | | | SCAC4 |
| 5284 | HUAU | HOEGH/UGLAND AUTOLINERS (HUAL) | | | SCAC1 |
| 5285 | HUAU | HOEGH/UGLAND AUTO LINERS, A/S | | | SCAC4 |
| 5286 | HUAV | HUNTER, AVERIL | | | SCAC4 |
| 5287 | HUAX | Huasteca Petroleum Co. | 7/1930-4/1938 | | NAKINA |
| 5288 | HUAX | Huasteca Petroleum Co. | Apr-38 | | NRHS |
| 5289 | HUAX | HUASTECA PETROLEUM CO. | | | PWRC |
| 5290 | HUB | Hub Airlines, Inc. | Callsign: Hub, | USA | AVCODES |
| 5291 | HUB | Hub Airlines | | | ICAO1 |
| 5292 | HUB | HUDSON BUS LINES | | | SCAC4 |
| 5293 | HUBA | Hudson Bay | 1/1975-1/1980 | | NAKINA |
| 5294 | HUBA | Hudson Bay | 1/75-1/80 | | NRHS |
| 5295 | HUBA | BURLINGTON NORTHERN & SANTA FE RWY (BNSF) [HUDSON BAY CO. RR] | | | PWRC |
| 5296 | HUBA | Hudson Bay (BNSF Railway) | | | RSRV |
| 5297 | HUBB | HUB COMPUTER SOLUTIONS | | | SCAC4 |
| 5298 | HUBD | HUB DISPLAYWORKS INC | | | SCAC4 |
| 5299 | HUBERT | J. Hubert GmbH | | D | TRAFFIC |
| 5300 | HUBF | HUB FREIGHT USA INC | | | SCAC4 |
