| 301 | DALIAN | Dalian Metro | | PRC | TRAFFIC |
| 302 | DALK | DAM ASSOCIATES LLC | | | SCAC4 |
| 303 | DALM | DALOMAR SHIPPING S A | | | SCAC4 |
| 304 | DALM | Acciaierie Dalmine | | I | TRAFFIC |
| 305 | DALMINE | Dalmine Steel Works | | I | TRAFFIC |
| 306 | DALP | DALPE, JOCELYN TRANSPORT INC | | | SCAC4 |
| 307 | DALS | DALE, ALLAN INDUSTRIES LTD | | | SCAC4 |
| 308 | DALT | Dallas Terminal Ry. | added 7/2004; eliminated 10/2004; 7/2005 | | NAKINA |
| 309 | DALT | DALLAS TERMINAL RAILWAY | | | PWRC |
| 310 | DALT | Dallas Terminal Railway | | | RSRV |
| 311 | DALT | DALLAS TERMINAL RAILWAY | | | SCAC4 |
| 312 | DALU | D'AMICO SOC DI NAVIGAZIONE | | | SCAC1 |
| 313 | DALU | CP SHIPS | | | SCAC4 |
| 314 | DALX | Dominion Alkali & Chemical Co., Ltd. | 1/1950-1/1952; eliminated 4/1953 | | NAKINA |
| 315 | DALX | Daly Refining Co. | 7/1937-1/1945; 1/1946 (not listed) | | NAKINA |
| 316 | DALX | Daly Refining Co. | Apr-38 | | NRHS |
| 317 | DALX | Dominion Alkali & Chemical Co., Ltd. | Jan-52 | | NRHS |
| 318 | DALX | *DALY REFINING CO. | | | PWRC |
| 319 | DALX | *DOMINION ALKALI & CHEMICAL CO. LTD. | | | PWRC |
| 320 | DALY | DAILY MOTOR FREIGHT, INC | | | SCAC1 |
| 321 | DALY | D & A LOGISTICS LLC | | | SCAC4 |
| 322 | DALZ | D & A LEASING INC. | | | PWRC |
| 323 | DALZ | D and A Leasing | | | RSRV |
| 324 | DALZ | D & A LEASING INC | | | SCAC4 |
| 325 | DAM | DAMES, Department of aviation under the Ministry of Emergency Situaion | Callsign: Flight Rescue, Ceased operations. | KS | AVCODES |
| 326 | DAM | Kyrgyzstan Department of Aviation | | | ICAO1 |
| 327 | DAMA | D'AMATO DI NAVIGAZIONE SPA | | | SCAC4 |
| 328 | DAMD | DAMCO INTERNATIONAL TRANSPORTATION | | | SCAC4 |
| 329 | DAMH | DE ANDA MOJICA, HEDER AXEL | | | SCAC4 |
| 330 | DAMI | D'AMICO SHIPPING ITALIA SPA | | | SCAC4 |
| 331 | DAML | D'AMICO | | | SCAC1 |
| 332 | DAML | DIAMLEMOS SHIPPING CORPORATION | | | SCAC4 |
| 333 | DAMO | DE ANDA MOJICA, FELIPE DE JESUS | | | SCAC4 |
| 334 | DAMQ | D A M EXPRESS | | | SCAC4 |
| 335 | DAMT | D'AMICO TANKERS LIMITED | | | SCAC4 |
| 336 | DAMU | CARU CONTAINERS BV | | NL | BIC |
| 337 | DAMU | DAMCO MARITIME | | | SCAC1 |
| 338 | DAMX | Dewey & Almy Chemical Co. (Merchants Despatch, Inc.) | 7/1935 | | NAKINA |
| 339 | DAN | Maersk Air A/S | IATA: DM, Callsign: Maerskair, IATA Prefix: 349, Merged into Sterling | DK | AVCODES |
| 340 | DAN | Dan-Air Services Ltd. | IATA: DA, Callsign: Danair, Merged into British Airways European Operations Gatwick B.A.E.O.G. | GB | AVCODES |
| 341 | DAN | Air Georgia | IATA: DA, Callsign: Air Georgia, Merged into Aircompany Airzena Georgian Airlines. Designator DA recalled by IATA | GE | AVCODES |
| 342 | DAN | Dana Airlines Ltd. | IATA: 9J, Callsign: Dana Air, ICAO code changedfrom DAV | WAN | AVCODES |
| 343 | DAN | DSB aarhus Nærbane A/S | | DK | VKM |
| 344 | DANA | DANIELS, ANDREW | | | SCAC4 |
| 345 | DANAN | Da-Nan Bus | City: Taipei | RC | TRAFFIC |
| 346 | DANB | DAY AND NIGHT SERVICES INC | | | SCAC4 |
| 347 | DANF | DANISI FUEL CO INC | | | SCAC4 |
| 348 | DANG | DANGO INC | | | SCAC4 |
| 349 | DANI | DANISA TRANSPORT | | | SCAC4 |
| 350 | DANN | DANA TRANSPORT SYSTEMS INC | | | SCAC4 |
| 351 | DANO | DOC AND NORM DIRECT LLC | | | SCAC4 |
| 352 | DANQ | DERINGER, A N INC | | | SCAC4 |
| 353 | DANR | DARVONDA NURSERIES LTD | | | SCAC4 |
| 354 | DANS | DANIEL MOVING SYSTEM INC | | | SCAC4 |
| 355 | DANU | DONATI SPEDITION S.R.L. | | I | BIC |
| 356 | DANUB | Logistic Services Danubius | since 2011 DB Schenker Rail Romania | RO | TRAFFIC |
| 357 | DANV | DERINGER, A N INC | | | SCAC4 |
| 358 | DANX | Danville Industries, Inc. | added 1/1974; 1/1975-1/1980; eliminated 4/1982 | | NAKINA |
| 359 | DANX | Danville Industries, Inc. | added 1/74; 1/75-1/80; eliminated 4/82 | | NRHS |
| 360 | DANX | DANVILLE INDUSTRIES, INC. | | | PWRC |
| 361 | DANY | DANYRO TRANSPORT ENR | | | SCAC4 |
| 362 | DAO | Daallo Airlines | IATA: D3, Callsign: Dalo Airlines, IATA Prefix: 991, | DJI | AVCODES |
| 363 | DAO | Daallo Airlines | IATA: D3 | | ICAO1 |
| 364 | DAOI | DAO TRUCKING | | | SCAC4 |
| 365 | DAOL | DAO TRANSPORT LLC | | | SCAC4 |
| 366 | DAON | DAVIS OIL INC | | | SCAC4 |
| 367 | DAOO | DAOU AUTO SALES | | | SCAC4 |
| 368 | DAP | Aerovias DAP | | | ICAO1 |
| 369 | DAPA | PARKER, D A TRUCKING | | | SCAC4 |
| 370 | DAPL | Dampf-Plus GmbH | | D | TRAFFIC |
| 371 | DAPP | DURATEX APPAREL | | | SCAC4 |
| 372 | DAPT | DEPENDABLE AUTO SHIPPERS INC | | | SCAC4 |
| 373 | DAPX | Dairyland Power Cooperative | added 10/1979; 1/1980-7/2005 | | NAKINA |
| 374 | DAPX | Dairyland Power Cooperative | 1/80-7/2000 | | NRHS |
| 375 | DAPX | DAIRYLAND POWER COOPERATIVE | | | PWRC |
| 376 | DAPX | Dairyland Power Cooperative | | | RSRV |
| 377 | DAPX | DAIRYLAND POWER COOPERATIVE | | | SCAC4 |
| 378 | DAQV | DAVIS, EDWIN TRUCKING INC | | | SCAC4 |
| 379 | DAR | Danish Army | Callsign: Danish Army, | DK | AVCODES |
| 380 | DAR | Danish Army | | | ICAO1 |
| 381 | DARD | DART LOGISTICS A DIVISION OF DART T | | | SCAC4 |
| 382 | DARD | Dardenne Reisen | | D | TRAFFIC |
| 383 | DARE | DAVIS, RONALD E | | | SCAC4 |
| 384 | DARG | D & A TRUCKING | | | SCAC4 |
| 385 | DARJ | Darjeeling Himalayan Railway | | IND | TRAFFIC |
| 386 | DARK | DARK STAR TRANSPORTATION CO LLC | | | SCAC4 |
| 387 | DARKANU | Darkanu Bus Corporation | | US-NJ | TRAFFIC |
| 388 | DARL | DARLING TRANSFER INC | | | PWRC |
| 389 | DARL | DARLING OIL & TIRE | | | SCAC4 |
| 390 | DARN | DART DEDICATED - ANDERSON (DIV OF D | | | SCAC4 |
| 391 | DARO | DELTA AERO | | | SCAC4 |
| 392 | DART | DALLAS AREA RAPID TRANSIT | | | PWRC |
| 393 | DART | DART TRANSIT COMPANY | | | SCAC4 |
| 394 | DART | Dallas Area Rapid Transit | City: Dallas | US-TX | TRAFFIC |
| 395 | DARTFS | DART First State (Delaware Transit Corporation) | | USA | TRAFFIC |
| 396 | DARU | DART CONTAINER LINE INC. | | | PWRC |
| 397 | DARU | Dart Container Line | | | RSRV |
| 398 | DARW | DARROW FOUNDATION | | | SCAC4 |
| 399 | DARZ | *DART INTERMODAL, INC. | | | PWRC |
| 400 | DARZ | *DELTA RAIL CORPORATION | | | PWRC |
