| 4501 | KREF | | City: Krefeld | D | TRAFFIC |
| 4502 | KREG | KRIEG BOYS ICE CORP | | | SCAC3 |
| 4503 | KREI | KRETH INC | | | SCAC3 |
| 4504 | KREJ | KRAMER, ELIOTT J | | | SCAC3 |
| 4505 | KREK | KRETTLER KARTAGE | | | SCAC3 |
| 4506 | KREM | Kremikovtzi AD | | BG | VKM |
| 4507 | KREN | KARENS TRANSPORTATION INC | | | SCAC3 |
| 4508 | KREQ | KRESS, R E EXPRESS | | | SCAC3 |
| 4509 | KRER | KREIDER, NOAH W & SONS | | | SCAC3 |
| 4510 | KRES | KRESSER MOTOR SERVICE INC | | | SCAC3 |
| 4511 | KRET | KREISER TRANSPORT | | | SCAC4 |
| 4512 | KREY | KREITZ MOTOR EXPRESS, INC | | | SCAC3 |
| 4513 | KREY | KMX INTERNATIONAL | | | SCAC4 |
| 4514 | KRF | UK Royal / VIP Flights (in military aircraft) | Callsign: Kittyhawk, | GB | AVCODES |
| 4515 | KRF | United Kingdom Royal VIP Flights | | | ICAO1 |
| 4516 | KRFN | KRAFT FOODS GLOBAL INC | | | SCAC4 |
| 4517 | KRFR | KEEN RIDGE FARMS | | | SCAC4 |
| 4518 | KRFT | KRAFT, BEN TRUCKING | | | SCAC3 |
| 4519 | KRFT | KEARFOTT PRECISIONES GENERALES DE M | | | SCAC4 |
| 4520 | KRFX | Kraft Foods, a Division of National Dairy Products Corp. | added 7/1958; eliminated 4/1961; added 7/1961; eliminated 1/1962 | | NAKINA |
| 4521 | KRFX | Kraft Foods, a Division of National Dairy Products Corp. | added 7/58; eliminated 4/61; eliminated 1/62 | | NRHS |
| 4522 | KRFX | KRAFT FOODS, DIV. NATIONAL DAIRY PRODUCTS CORP. | | | PWRC |
| 4523 | KRFX | Kraft Foods, a division of National Dairy Products Corp. | | USA | TRAFFIC |
| 4524 | KRG | Krimaviamontag | Callsign: Aviamontag, Ceased operations. | UA | AVCODES |
| 4525 | KRG | Krimaviamontag | | | ICAO1 |
| 4526 | KRGB | KRIGBAUM TRUCKING INC | | | SCAC3 |
| 4527 | KRGE | KROGER GRAIN | | | SCAC3 |
| 4528 | KRGF | KAY, R G FUEL OIL INC | | | SCAC4 |
| 4529 | KRGL | KROGEL AIR FREIGHT SERVICE, INC | | | SCAC3 |
| 4530 | KRGN | KIRCHGESSNER TRUCKING | | | SCAC3 |
| 4531 | KRGO | KARGO MAX TRAILER ENCLOSURES LTD | | | SCAC4 |
| 4532 | KRGP | KARGO TRANSPORTATION INC | | | SCAC4 |
| 4533 | KRGR | KRUGER TRUCKING | | | SCAC3 |
| 4534 | KRGS | KRINGS TRUCKING | | | SCAC3 |
| 4535 | KRGT | KRIEGSMAN TRANSFER CO | | | SCAC3 |
| 4536 | KRGU | KYRGYZSTANIAN RAILWAY ADMINISTRATIO | | | SCAC4 |
| 4537 | KRH | UK Royal / VIP Flights (in civil chartered aircraft) | Callsign: Sparrowhawk, | GB | AVCODES |
| 4538 | KRH | United Kingdom Royal VIP Flight | | | ICAO1 |
| 4539 | KRHC | KRAMER, H & CO | | | SCAC3 |
| 4540 | KRHD | KARCHER, RICHARD T | | | SCAC3 |
| 4541 | KRHF | KROEGER, H F | | | SCAC3 |
| 4542 | KRHG | KELLY, RON HAULING INC | | | SCAC3 |
| 4543 | KRHI | KREUSCH, LEONARD INC | | | SCAC3 |
| 4544 | KRHI | KERRS HOME PRODUCT LIMITED | | | SCAC4 |
| 4545 | KRHL | KRAHL TRANSPORT INC | | | SCAC4 |
| 4546 | KRHN | KROHN LOGGING INC | | | SCAC3 |
| 4547 | KRHQ | KROHN CARTAGE CO INC | | | SCAC3 |
| 4548 | KRHT | KRISTICH, MARTIN TRUCKING | | | SCAC3 |
| 4549 | KRI | Krylo Airlines | IATA: K9, Callsign: Krilo, | RUS | AVCODES |
| 4550 | KRI | Krylo Airlines | IATA: K9 | | ICAO1 |
| 4551 | KRIA | KRISAX | | | SCAC4 |
| 4552 | KRIG | K-RICH TRUCKING INC | | | SCAC4 |
| 4553 | KRII | KRIEG, ALBERTA L | | | SCAC3 |
| 4554 | KRIL | KERR INDUSTRIES LTD | | | SCAC3 |
| 4555 | KRIMTR | Krymtrolleybus | | UA | TRAFFIC |
| 4556 | KRIN | KRIC | | | SCAC3 |
| 4557 | KRIN | KELLY-RYAN INC | | | SCAC4 |
| 4558 | KRIQ | KRICKL MOTOR SERVICE | | | SCAC3 |
| 4559 | KRIS | Kris-Tour ABC | | PL | TRAFFIC |
| 4560 | KRITT | Manfred Kritter | | DE | VKM |
| 4561 | KRIU | KRICON SERVICES B.V. | | NL | BIC |
| 4562 | KRIX | General Electric Rail Services Corp. | added 1/2000; 7/2000-7/2005 | | NAKINA |
| 4563 | KRIX | General Electric Railcar Services Corp. | added 10/1998; eliminated 1/2000 | | NAKINA |
| 4564 | KRIX | Kyle Rys., Inc. | added 4/1996; eliminated 10/1998 | | NAKINA |
| 4565 | KRIX | Kyle Rys., Inc. | added 4/96; eliminated 10/98 | | NRHS |
| 4566 | KRIX | General Electric Railcar Services Corp. | added 10/98; eliminated 1/2000 | | NRHS |
| 4567 | KRIX | General Electric Rail Services Corp. | added 1/2000; 7/2000 | | NRHS |
| 4568 | KRIX | GENERAL ELECTRIC RAIL SERVICES (KYLE RWYS., INC.) | | | PWRC |
| 4569 | KRIX | Kyle Railways (GE Rail Services Corporation) | | | RSRV |
| 4570 | KRIX | GENERAL ELECTRIC RAILCAR SERVICES C | | | SCAC4 |
| 4571 | KRIZ | KRAMER INDUSTRY | | | PWRC |
| 4572 | KRIZ | KNIGHTS TRANSPORTATION SERVICES INC | | | SCAC4 |
| 4573 | KRJ | Klippan - Röstånga Järnväg | 1892 - 1898 | S | svenska-lok.se |
| 4574 | KRJA | KARIJA ARABIANS | | | SCAC4 |
| 4575 | KRJJ | KRONENBERG, JAMES JOSEPH | | | SCAC3 |
| 4576 | KRJK | KRAJICEK INC | | | SCAC4 |
| 4577 | KRJS | K R J SYSTEMS INC | | | SCAC3 |
| 4578 | KRJT | KEENE, ROBERT J TRUCKING INC | | | SCAC3 |
| 4579 | KRKC | KNEDLER TRUCKING | | | SCAC3 |
| 4580 | KRKF | KIRKEY RACING FABRICATION INC | | | SCAC4 |
| 4581 | KRKG | KARENS KARTAGE INC | | | SCAC3 |
| 4582 | KRKG | KLAIR TRUCKING | | | SCAC4 |
| 4583 | KRKI | KIRK TRUCKING INC | | | SCAC3 |
| 4584 | KRKK | KROGH, KEN K | | | SCAC3 |
| 4585 | KRKL | KIRK, LARRY TRUCKING | | | SCAC3 |
| 4586 | KRKN | K & R TRUCKING INC | | | SCAC3 |
| 4587 | KRKO | KRISTYS KORNER | | | SCAC3 |
| 4588 | KRKQ | KERKYRA SHIPPING COMPANY | | | SCAC3 |
| 4589 | KRKT | KIRK TRUCKING | | | SCAC4 |
| 4590 | KRKY | KIRKSEY TRUCKING INC | | | SCAC4 |
| 4591 | KRL | Kryla | Callsign: Citadel Air, Ceased operations. | UA | AVCODES |
| 4592 | KRL | Kasgro Rail Lines | added 10/2000; 7/2005 | | NAKINA |
| 4593 | KRL | Kasgro Rail Lines | added 10/2000 | | NRHS |
| 4594 | KRL | KASGRO RAIL LINES | | | PWRC |
| 4595 | KRL | Kasgro Rail Lines | | | RSRV |
| 4596 | KRL | KASGRO RAIL LINES | | | SCAC4 |
| 4597 | KRLA | KESTER RACING LLC | | | SCAC4 |
| 4598 | KRLC | KISTNER RESOURCES LLC | | | SCAC4 |
| 4599 | KRLG | K & R LOG & LUMBER CO INC | | | SCAC3 |
| 4600 | KRLK | KREILKAMP TRUCKING, INC | | | SCAC3 |
