| 501 | DAX | Diamond Alkali Co. | 7/1930-10/1966; eliminated 4/1968 | | NAKINA |
| 502 | DAX | Diamond Alkali Co. | 4/38-10/66; eliminated 4/68 | | NRHS |
| 503 | DAX | Diamond Shamrock Corp. | added 4/68; 4/70-1/80 | | NRHS |
| 504 | DAX | Diamond Shamrock Chemicals Co. | eliminated 7/87 | | NRHS |
| 505 | DAX | Occidental Chemical Corp., Electrochemicals, Detergents & Specialty Products Group | added 7/87; eliminated 1/88 | | NRHS |
| 506 | DAX | Occidental Chemical Corp., Electrochemicals, Detergents & Specialty Products | added 1/88; eliminated 10/89 | | NRHS |
| 507 | DAX | Occidental Chemical Corp., Electrochemicals & Specialty Products | added 10/89; eliminated 1/92 | | NRHS |
| 508 | DAX | Occidental Chemical Corp. | added 1/92; 1/94-7/2000 | | NRHS |
| 509 | DAX | *DIAMOND SHAMROCK CHEMICALS CO. [DIAMOND ALKALI CO.] | | | PWRC |
| 510 | DAX | +OCCIDENTAL CHEMICAL CORP., ELECTROCHEMICALS & SPECIALTY PRODUCTS | | | PWRC |
| 511 | DAX | Diamond Shamrock Chemicals (Occidental Chemical Corporation) | | | RSRV |
| 512 | DAX | OCCIDENTAL CHEMICAL CORPORATION | | | SCAC4 |
| 513 | DAXI | DAXI SA | | RO | VKM |
| 514 | DAXL | DEFINED AIR XPRESS LLC | | | SCAC4 |
| 515 | DAXT | DAX TRUCKING | | | SCAC4 |
| 516 | DAXU | NAVIERA DIRECT AFRICA LINE S.A | | E | BIC |
| 517 | DAY | Daya Aviation (Pvt) Ltd | Callsign: Daya, | CL | AVCODES |
| 518 | DAY | Daya Aviation | | | ICAO1 |
| 519 | DAYA | DAYMOND ALUMINUM | | | SCAC4 |
| 520 | DAYE | DAYRUNNER | | | SCAC4 |
| 521 | DAYF | DAYTON TRANSFER INC | | | SCAC4 |
| 522 | DAYG | DAY TRUCKING INC | | | SCAC4 |
| 523 | DAYL | DAY, RONALD L TRANSPORTATION INC | | | SCAC4 |
| 524 | DAYN | DAY OR NITE EXPRESS INC | | | SCAC4 |
| 525 | DAYO | DAYUS REGISTER AND GRILLE INC | | | SCAC4 |
| 526 | DAYP | DAY & NIGHT TRANSPORT INC | | | SCAC4 |
| 527 | DAYQ | DAYSTAR TRANSPORTATION LLC | | | SCAC4 |
| 528 | DAYR | DAY&ROSS INC | | | SCAC1 |
| 529 | DAYR | DAY & ROSS INC | | | SCAC4 |
| 530 | DAYT | DAY, H. A | | | SCAC1 |
| 531 | DAYU | HAPAG LLOYD A.G | | D | BIC |
| 532 | DAYU | DEUTSCHE AFRIKA LINIEN GMBH & CO | | | SCAC4 |
| 533 | DAYW | DAY, WILLIS, MOVING & STORAGE CO | | | SCAC1 |
| 534 | DAYW | DAY, WILLIS MOVING & STORAGE CO | | | SCAC4 |
| 535 | DAYY | DAY TRANSFER COMPANY | | | SCAC4 |
| 536 | DAZ | DAS Air Limited | IATA: WD, Callsign: Dasair, IATA Prefix: 761, Name changed to Dairo Air Service Ltd. IATA code changed from SE* | EAK | AVCODES |
| 537 | DAZ | Hala Fly Airlines | Callsign: Hala, | SYR | AVCODES |
| 538 | DAZA | DANZEL AIR FREIGHT INC | | | SCAC4 |
| 539 | DAZC | DULCERIA AZTECA | | | SCAC4 |
| 540 | DAZE | DAZE TRANSFER & STORAGE CO | | | SCAC4 |
| 541 | DAZJ | DIAZ, JESS, TRUCKING, INC | | | SCAC1 |
| 542 | DAZJ | DIAZ, JESS TRUCKING INC | | | SCAC4 |
| 543 | DAZL | DELTA TRANZ LLC | | | SCAC4 |
| 544 | DAZM | DANTZLER INC | | | SCAC4 |
| 545 | DAZT | DIAZ TRUCKING | | | SCAC4 |
| 546 | DB | Brit Air | ICAO: BZH, Callsign: Britair, IATA Prefix: 750, Name changed to Brit Air t/a HOP! Brit Air. Name changed from Brittany Air International | F | AVCODES |
| 547 | DB | Air Niagara Express, Inc. | ICAO: DBD, Callsign: Air Niagara, | CDN | AVCODES |
| 548 | DB | Bulair | Callsign: Bulair, | BG | AVCODES |
| 549 | DB | Air Niagara (1978) Limited | ICAO: DBD, Callsign: Databird, | CDN | AVCODES |
| 550 | DB | Execaire Aviation Ltd. | ICAO: EXA, Callsign: Canadian Execaire, | CDN | AVCODES |
| 551 | DB | Brit Air t/a HOP! Brit Air | ICAO: BZH, Callsign: Britair, IATA Prefix: 750, Name changed from Brit Air. Name changed from Brittany Air International | F | AVCODES |
| 552 | DB | Maleth-Aero AOC Ltd | ICAO: MLT, Callsign: Maleth, IATA Prefix: 094, Name changed from Hangar 8 AOC Malta Limited t/a Maleth-Aero | M | AVCODES |
| 553 | DB | RETIRED 04-22-93 ATP | | | PWRC |
| 554 | DB | Deutsche Bundesbahn | | D | TRAFFIC |
| 555 | DB | Deutsche Bahn / DB AG | | DE | VKM |
| 556 | DB M | DB Museum Nürnberg | Nürnberg | D | privat-bahn.de |
| 557 | DBA | Air Alpha, Inc. | Callsign: Double-A, | USA | AVCODES |
| 558 | DBA | Air Alpha | | | ICAO1 |
| 559 | DBAB | DENO, BRIAN TRUCKING | | | SCAC4 |
| 560 | DBAC | DOUBLE A TRANSPORTATION LLC | | | SCAC4 |
| 561 | DBAF | DRY BULK AFRICA LTD | | | SCAC4 |
| 562 | DBAG | Deutsche Bahn AG. | | D | TRAFFIC |
| 563 | DBAK | DAKOTA BUCKAROO LLC | | | SCAC4 |
| 564 | DBAM | D AND B TRANSPORTATION COMPANY LLC | | | SCAC4 |
| 565 | DBAO | DEL-BO LOGISTICS | | | SCAC4 |
| 566 | DBAT | DUBOSE, JOHN M TRUCKING LLC | | | SCAC4 |
| 567 | DBB | Deutsche Bahn AG | IATA: 2A, Railway Service | D | AVCODES |
| 568 | DBB | DB Bahnbau | | D | TRAFFIC |
| 569 | DBBC | DAKOTA BEST BROKERAGE LLC | | | SCAC4 |
| 570 | DBBK | DOUBLE B BROKERAGE INC | | | SCAC4 |
| 571 | DBBL | DIBBLE TRUCKING INC | | | SCAC4 |
| 572 | DBBR | DOUBLE B BROKERAGE LLC | | | SCAC4 |
| 573 | DBBS | DOUBLE B SPECIALIZED CARRIERS LLC | | | SCAC4 |
| 574 | DBBV | D & B BUS INC | | | SCAC4 |
| 575 | DBC | Gemini Air Group, Inc. | Callsign: Diamond Back, | USA | AVCODES |
| 576 | DBC | DB Cargo | | D | TRAFFIC |
| 577 | DBCE | DBC ENTERPRISES INC | | | SCAC4 |
| 578 | DBCI | D-B CARTAGE INC | | | SCAC4 |
| 579 | DBCI | DB Cargo Italia | | I | TRAFFIC |
| 580 | DBCK | DIAMONDBACK EXPRESS INC | | | SCAC4 |
| 581 | DBCR | Deutsche Bahn Cargo Romania S.R.L. | | RO | TRAFFIC |
| 582 | DBCS | DORSETT BROTHERS CONCRETE SUPPLY | | | SCAC4 |
| 583 | DBCU | DRY BOX INC | | USA | BIC |
| 584 | DBCU | Dry Box | | | RSRV |
| 585 | DBCX | BASF Corp. | added 4/1986; 1/1994-7/2005 | | NAKINA |
| 586 | DBCX | Badische Corp. | added 7/1979; 1/1980; eliminated 4/1986; 1/1994 | | NAKINA |
| 587 | DBCX | Dow Badische Co. | added 1/1973; 1/1975; eliminated 7/1979 | | NAKINA |
| 588 | DBCX | Dowdle Brothers' Co. | 7/1930-7/1932 | | NAKINA |
| 589 | DBCX | Badische Corp. | added 7/79; 1/80; eliminated 4/86; 1/94 | | NRHS |
| 590 | DBCX | Dow Badische Co. | added 1/73; 1/75; eliminated 7/79 | | NRHS |
| 591 | DBCX | BASF Corp. | added 4/86; 1/94-7/2000 | | NRHS |
| 592 | DBCX | BASF CORPORATION [BADISCHE CORP.; DOW BADISCHE CO.; DOWDLE BROTHERS' CO.] | | | PWRC |
| 593 | DBCX | Dow Badische Corporation (BASF Corporation) | | | RSRV |
| 594 | DBCX | BASF CORPORATION | | | SCAC4 |
| 595 | DBCY | DELTA BROKERAGE COMPANY INC | | | SCAC4 |
| 596 | DBD | Air Niagara Express, Inc. | IATA: DB, Callsign: Air Niagara, | CDN | AVCODES |
| 597 | DBD | Air Niagara (1978) Limited | IATA: DB, Callsign: Databird, | CDN | AVCODES |
| 598 | DBD | Air Niagara Express | | | ICAO1 |
| 599 | DBDA | DOUBLE D TRUCKING | | | SCAC4 |
| 600 | DBDC | DB DISTRIBUTING INC | | | SCAC4 |
