| 501 | KAYS | KAYS TRANSPORT INC | | | SCAC4 |
| 502 | KAYT | KTN TRUCKING CORPORATION | | | SCAC4 |
| 503 | KAYU | KALYANI CAST TECH LTD | | IND | BIC |
| 504 | KAYV | KAYTEC VINYL INC | | | SCAC4 |
| 505 | KAZ | Tatarstan State Enterprise Aircompany | IATA: U9, Callsign: Air Tatarstan, IATA Prefix: 966, Name changed to Tatarstan JSC Aircompany | RUS | AVCODES |
| 506 | KAZ | Kazan Airenterprise (Tatarstan Airlines) | IATA: 4U, Callsign: Air Tatarstan, | RUS | AVCODES |
| 507 | KAZ | JSC Comluc KZ | Callsign: Kazlux, | KZ | AVCODES |
| 508 | KAZ | KNIGHT ARNOLD | | | PWRC |
| 509 | KAZA | KAZARIAN, MIKE | | | SCAC3 |
| 510 | KAZAN2 | Passenger motor transport enterprise No. 2, Kazan | City: Kazan | RUS | TRAFFIC |
| 511 | KAZD | K A Z DELIVERY SYSTEMS | | | SCAC3 |
| 512 | KAZD | Kaliningrad Railway | Real: KZD | RU | TRAFFIC |
| 513 | KAZJ | KATZMAN, J KENNETH JR INC | | | SCAC3 |
| 514 | KAZK | KAZAK BROTHERS INC | | | SCAC3 |
| 515 | KAZR | KAZIMOUR, ROBERT F | | | SCAC3 |
| 516 | KAZU | JSC KUIBYSHEV AZOT | | RUS | BIC |
| 517 | KAZU | KUIBYSHEVAZOT JSCV | | | SCAC4 |
| 518 | KB | Druk Air Corporation Ltd. | ICAO: DRK, Callsign: Royal Bhutan, IATA Prefix: 787, | BTN | AVCODES |
| 519 | KB | Burnthills Aviation Ltd. | | GB | AVCODES |
| 520 | KB | Kenya Aircharters Limited | Callsign: Kencharter, | EAK | AVCODES |
| 521 | KB | Cadabo Gestione Servizi Aeronautici | Callsign: Cadabo, | I | AVCODES |
| 522 | KB | Kalvehavebanen | 1897 - 1959 | DK | jernbanen.dk |
| 523 | KB | Kalvehavebanen | 1897 - 1959 | DK | TRAFFIC |
| 524 | KB | Kullmann Bauservice GmbH | | DE | VKM |
| 525 | KBA | Kenn Borek Air Ltd. | IATA: 4K, Callsign: Borek Air, Designator 4K recalled by IATA | CDN | AVCODES |
| 526 | KBA | Kenn Borek Air Ltd. | Callsign: Borek Air, Designator 4K recalled by IATA | CDN | AVCODES |
| 527 | KBA | Kenn Borek Air | | | ICAO1 |
| 528 | KBAA | K & B LOGISTICS LLC | | | SCAC4 |
| 529 | KBAD | KLASSEN, BILL AUCTIONS LTD | | | SCAC4 |
| 530 | KBAL | KOLB, AL TRUCKING | | | SCAC3 |
| 531 | KBAP | KB TRANSPORTATION | | | SCAC4 |
| 532 | KBAQ | KILLEBREW, BOB A | | | SCAC3 |
| 533 | KBAQ | KILLEBREW TRUCKING SERVICE | | | SCAC4 |
| 534 | KBB | Deutsche Gesellschaft für Eisenbahngeschichte e.V | | DE | VKM |
| 535 | KBBG | K B BROKERAGE | | | SCAC4 |
| 536 | KBBS | KBBS CONVOY | | | SCAC3 |
| 537 | KBBS | KB FREIGHT SYSTEMS | | | SCAC4 |
| 538 | KBBT | KERBS BROS TRUCKING | | | SCAC3 |
| 539 | KBBT | KBK TRANSPORTES | | | SCAC4 |
| 540 | KBC | KERRVILLE BUS COMPANY | | | SCAC4 |
| 541 | KBC | Kobe Municipal Subway | | J | TRAFFIC |
| 542 | KBCA | KC BUILDERS COMPANY LLC | | | SCAC4 |
| 543 | KBCI | KELLEY BROTHERS CONTRACTORS INC | | | SCAC3 |
| 544 | KBCO | KABECO (DIV AMERICAN TRANSPORT INC) | | | SCAC3 |
| 545 | KBCP | K B COMPANY INC | | | SCAC3 |
| 546 | KBCQ | KIMBLE CARTAGE INC | | | SCAC4 |
| 547 | KBCT | KNAPP, BRUCE C TRUCKING | | | SCAC3 |
| 548 | KBCT | KBC TOOLS INC | | | SCAC4 |
| 549 | KBCZ | KELLEY BEAN COMPANY | | | PWRC |
| 550 | KBD | JetKey | Callsign: Jet Key, | F | AVCODES |
| 551 | KBDS | KBD SERVICES INC | | | SCAC3 |
| 552 | KBDS | KIRBY, DAVE TRANSPORT INC | | | SCAC4 |
| 553 | KBE | Köln-Bonner Eisenbahnen AG | City: Köln | D | TRAFFIC |
| 554 | KBEC | Kent, Barry, Eaton Connecting Ry., Inc. | added 4/1980; eliminated 1/1984 | | NAKINA |
| 555 | KBEC | Kent, Barry, Eaton Connecting Ry., Inc. | added 4/80 | | NRHS |
| 556 | KBEC | KENT, BARRY, EATON CONNECTING RAILWAY CO. | | | PWRC |
| 557 | KBEF | Köln-Bonner Eisenbahnfreunde e.V. | Köln | D | privat-bahn.de |
| 558 | KBEF | Köln-Bonner Eisenbahn -Freunde e.V | | DE | VKM |
| 559 | KBEI | K B EXPRESS INC | | | SCAC4 |
| 560 | KBEL | KBEL TRANSPORT | | | SCAC4 |
| 561 | KBEN | KREITZ, J & H TRANSPORT | | | SCAC4 |
| 562 | KBEP | KB EXPRESS | | | SCAC4 |
| 563 | KBEV | KINGSBURY ELEVATOR INC | | | SCAC4 |
| 564 | KBF | Korsnäs AB, Produktion Frövi | | SE | VKM |
| 565 | KBFC | KLEBE FUEL CO INC | | | SCAC4 |
| 566 | KBFL | K & B FREIGHT LINE | | | SCAC3 |
| 567 | KBFL | K B CORPORATION | | | SCAC4 |
| 568 | KBFP | K B FUEL CORP | | | SCAC4 |
| 569 | KBFS | K&B FREIGHT SYSTEMS, AMJES, INC | | | SCAC3 |
| 570 | KBG | Korsnäs AB, Produktion Gävle | | SE | VKM |
| 571 | KBGA | KOMROWSKI | | | SCAC4 |
| 572 | KBGT | KLINGBERG TRUCKING INC | | | SCAC4 |
| 573 | KBHI | KBH INC | | | SCAC3 |
| 574 | KBHI | KEBO TRANSPORTATION SERVICES INCORP | | | SCAC4 |
| 575 | KBIB | KITS BROKERAGE INC | | | SCAC4 |
| 576 | KBIC | KENNAMER BROTHERS INC | | | SCAC4 |
| 577 | KBID | KNIGHT BROKERAGE LLC (INTERMODAL DI | | | SCAC4 |
| 578 | KBIM | KIRBY INLAND MARINE | | | SCAC4 |
| 579 | KBIN | KC BROTHERS INC | | | SCAC4 |
| 580 | KBJ | Kävlinge - Barsebäck Järnväg | 1907 - 1927 | S | svenska-lok.se |
| 581 | KBJS | KBJ SYSTEMS INC | | | SCAC4 |
| 582 | KBKF | KIMBROOKE FARM | | | SCAC4 |
| 583 | KBKO | KENNEDY BROTHERS INC | | | SCAC4 |
| 584 | KBKS | KISSEL CABBAGE CORPORATION | | | SCAC4 |
| 585 | KBKX | Carey, Baxter and Kennedy, Inc. | 7/1937-4/1961 (not listed) | | NAKINA |
| 586 | KBKX | Carey, Baxter and Kennedy, Inc. | 1/52-4/61 | | NRHS |
| 587 | KBKX | CAREY, BAXTER & KENNEDY, INC. | | | PWRC |
| 588 | KBL | Kabul Air Company | Callsign: Kabul Air, | AFG | AVCODES |
| 589 | KBL | Kleinbahn Leeste e.V. | Leeste | D | privat-bahn.de |
| 590 | KBL | KOBUSSEN BUSES LTD | | | SCAC4 |
| 591 | KBLF | KNOBLOCH FARMS TRUCKING INC | | | SCAC3 |
| 592 | KBLG | K B LOGISTICS INC | | | SCAC4 |
| 593 | KBLI | KLEEN BLAST DIVISION CANAM | | | SCAC4 |
| 594 | KBLM | KB LOGISTICS MANAGEMENT INC | | | SCAC4 |
| 595 | KBLP | KBL TRANSPORT INC | | | SCAC4 |
| 596 | KBLQ | K-BAR LIVESTOCK TRANSPORT INC | | | SCAC3 |
| 597 | KBLQ | KIMBALL FARM FEEDS 2 INC | | | SCAC4 |
| 598 | KBLR | KBL TRANSPORTATION INC | | | SCAC4 |
| 599 | KBLS | K B LEASING | | | SCAC3 |
| 600 | KBLT | KIMBERLAIN TRUCKING INC | | | SCAC3 |
