| 1 | K | Ansett Australia | | AUS | TRAFFIC |
| 2 | K&E | Kentwood & Eastern Ry. Co. | 8/1920 | | NAKINA |
| 3 | K&E | KENTWOOD & EASTERN RWY. CO. | | | PWRC |
| 4 | K&M | Kanawha & Michigan Ry. (New York Central R.R.) | 7/1930-7/1932 | | NAKINA |
| 5 | K&M | Kanawha & Michigan Ry. (New York Central R.R.—Ohio Central Lines) | 7/1923 | | NAKINA |
| 6 | K&M | Kanawha & Michigan Ry. Co. | 8/1920 | | NAKINA |
| 7 | K&M | NEW YORK CENTRAL RAILROAD [KANAWHA & MICHIGAN RWY. CO.] | | | PWRC |
| 8 | K&T | Kentucky & Tennessee Ry. | 7/1923-7/1936 | | NAKINA |
| 9 | K&T | KENTUCKY & TENNESSEE RAILWAY CO. | | | PWRC |
| 10 | K&WV | Kanawha & West Virginia R.R. (New York Central R.R.) | 7/1930 | | NAKINA |
| 11 | K&WV | Kanawha & West Virginia R.R. (New York Central R.R.—Ohio Central Lines) | 7/1923 | | NAKINA |
| 12 | K&WV | Kanawha & West Virginia R.R. Co. (Kanawha & Michigan Ry.) | 8/1920 | | NAKINA |
| 13 | K&WV | NEW YORK CENTRAL RAILROAD [KANAWHA & MICHIGAN RWY.; KANAWHA & WEST VIRGINIA RAILROAD CO.] | | | PWRC |
| 14 | K0 | Sunwing Airlines Inc | ICAO: SWG, IATA Prefix: 292, IATA designator changed to WG on 15 Aug 2006 | CDN | AVCODES |
| 15 | K1 | Topas Co. Ltd. | | ROK | AVCODES |
| 16 | K2 | Eurolot, S.A. | ICAO: ELO, Callsign: Eurolot, Founded in 1996. Ceased operations on 31 March 2015. | PL | AVCODES |
| 17 | K2 | Kyrghyzstan Airlines | ICAO: KGY, Callsign: Kyrair, IATA Prefix: 758, ICAO designator changed from KGA | KS | AVCODES |
| 18 | K2 | Kyrghyzstan Airlines | ICAO: KGA, Callsign: Kyrair, IATA Prefix: 758, ICAO designator changed to KGY | KS | AVCODES |
| 19 | K2 | Paklook Air, Inc. d/b/a Airlift Alaska | | USA | AVCODES |
| 20 | K3 | Taquan Air Services, Inc. | ICAO: TQN, Callsign: Taquan, Designator K3* recalled by IATA | USA | AVCODES |
| 21 | K3 | Venture Travel, LLC. t/a Taquan Air | ICAO: TQN, Callsign: Taquan, Designator K3* reinstated by IATA. IATA designator changed from H7* | USA | AVCODES |
| 22 | K3 | Ketchikan Air Serivce, Inc. | Ceased Operations. | USA | AVCODES |
| 23 | K3 | Safe Air Company Limited | ICAO: SAQ, Callsign: Sinbad, Name changed to SAC (K) Limited. | EAK | AVCODES |
| 24 | K3 | SAC (K) Limited | ICAO: SAQ, Callsign: Sinbad, IATA Prefix: 645, Name changed from Safe Air Company Limited. | EAK | AVCODES |
| 25 | K3F | Keolis 3 Frontières | | F | TRAFFIC |
| 26 | K4 | Kronflyg | Designator K4* recalled by IATA | S | AVCODES |
| 27 | K4 | Kazakhstan Airlines | ICAO: KZA, | KZ | AVCODES |
| 28 | K4 | Kalitta Air LLC | ICAO: CKS, Callsign: Connie, IATA designator changed from CB*. Name changed from Kitty Hawk International, Inc. d/b/a American International Airways | USA | AVCODES |
| 29 | K4 | ALS Ltd. | | EAK | AVCODES |
| 30 | K5 | Alaska Juneau Aeronautics Inc d/b/a Wings Of Alaska | ICAO: WAK, Callsign: Wings Alaska, Name changed to SeaPort Airlines, Inc. dba Wings of Alaska | USA | AVCODES |
| 31 | K5 | Aban Air | ICAO: ABE, IATA Prefix: 710, Designator K5 recalled by IATA | IR | AVCODES |
| 32 | K5 | Seaport Airlines, Inc. | ICAO: SQH, Callsign: Sasquatch, Ceased operations on 20 September 2016 and filed for Chapter 7 bankruptcy. Name changed from Alaska Juneau Aeronautics, Inc. | USA | AVCODES |
| 33 | K5 | SeaPort Airlines, Inc. dba Wings of Alaska | ICAO: WAK, Callsign: Wings Alaska, Name changed from Alaska Juneau Aeronautics Inc d/b/a Wings Of Alaska. Acquired by SeaPort Airlines in 2008 | USA | AVCODES |
| 34 | K5 | Silverstone Air Services Ltd | ICAO: SLR, Callsign: Silverstone, | EAK | AVCODES |
| 35 | K5 | Kalitta Charters II, LLC | ICAO: KII, Callsign: Dragster, | USA | AVCODES |
| 36 | K6 | Khalifa Airways | ICAO: KZW, Callsign: Khalifa Air, IATA Prefix: 122, Suspended operations on 04 April 2003. | DZ | AVCODES |
| 37 | K6 | Apollo Airlines, S.A. | ICAO: AOA, Callsign: Apollo Air, IATA designator changed from PJ | GR | AVCODES |
| 38 | K6 | Bravo Air Congo | ICAO: BBV, Founded in 2006. Ceased operations on 10 December 2007. | ZRE | AVCODES |
| 39 | K6 | Cambodia Angkor Air Ltd. | ICAO: KHV, Callsign: Cambodia Air, IATA Prefix: 188, | K | AVCODES |
| 40 | K7 | National Aircompany Sakha Avia | ICAO: IKT, Callsign: Sakha-Avia, IATA Prefix: 840, Designator K7 recalled by IATA | RUS | AVCODES |
| 41 | K7 | Carib Aviation Limited | ICAO: DEL, Callsign: Red Tail, Designator K7* recalled by IATA | AG | AVCODES |
| 42 | K7 | National Aircompany Sakha Avia | ICAO: IKT, Callsign: Sakha-Avia, IATA Prefix: 840, Designator K7 reinstated by IATA | RUS | AVCODES |
| 43 | K7 | Arizona Express Airlines, Inc. | ICAO: TMP, Callsign: Tempe, | USA | AVCODES |
| 44 | K7 | Air Almaty JSC | ICAO: LMY, IATA Prefix: 346, | KZ | AVCODES |
| 45 | K7 | KoralBlue Airlines | ICAO: KBR, Callsign: Koral Blue, Ceased operations 2011 | ET | AVCODES |
| 46 | K7 | Taron-Avia LLC | ICAO: TRV, Callsign: Taronavia, Designator K7* recalled by IATA | AM | AVCODES |
| 47 | K7 | Air KBZ Limited | ICAO: KBZ, Callsign: Jade Air, | MYA | AVCODES |
| 48 | K8 | Dutch Caribbean Airline N.V. | ICAO: DCE, Callsign: Dutch Caribbean, IATA Prefix: 559, | NA | AVCODES |
| 49 | K8 | Caribbean Sun Airlines, Inc. d/b/a World Atlantic Airlines | ICAO: WAL, Callsign: World Atlantic, Designator K8* recalled by IATA. Name changed from Caribbean Sun Airlines, Inc | USA | AVCODES |
| 50 | K8 | Caribbean Sun Airlines, Inc | ICAO: SFG, Name changed to Caribbean Sun Airlines, Inc. d/b/a World Atlantic Airlines | USA | AVCODES |
| 51 | K8 | Kannithi Aviation Company Limited d/b/a Kan Air | ICAO: KND, Callsign: Kannithi Air, | T | AVCODES |
| 52 | K8 | InterJet West, Inc. | ICAO: IJW, Callsign: Jet West, | USA | AVCODES |
| 53 | K9 | Skyward Aviation Ltd. | ICAO: SGK, Callsign: Skyward, Designator K9 reinstated by IATA | CDN | AVCODES |
| 54 | K9 | Krylo Airlines | ICAO: KRI, Callsign: Krilo, | RUS | AVCODES |
| 55 | K9 | Itapemirim Transportes Aereos S.A. | ICAO: ITM, IATA designator changed to 5W*. Branded as Itapemirim Cargo. | BR | AVCODES |
| 56 | K9 | Kalitta Charters LLC | ICAO: KFS, Callsign: Kalitta, | USA | AVCODES |
| 57 | K9 | Aircompany "Esen Air" | ICAO: ESD, Callsign: Esen Air, Founded in 2006. Ceased operations in 2008. | KS | AVCODES |
| 58 | K9 | Tonlesap Airlines | ICAO: TSP, Callsign: Tonlesap Air, IATA Prefix: 443, Founded in 2011. Ceased operations in 2013. | K | AVCODES |
| 59 | K9 | Krasavia, State Enterprise of Krasnoyarsk Territory | ICAO: SSJ, Callsign: Siberian Sky, Designator K9 recalled by IATA | RUS | AVCODES |
| 60 | KA | Hong Kong Dragon Airlines Limited t/a Dragonair | ICAO: HDA, Callsign: Dragonair, IATA Prefix: 043, ICAO callsign changed to Dragon | HK | AVCODES |
| 61 | KA | Kalinga Airlines | | IND | AVCODES |
| 62 | KA | Hong Kong Dragon Airlines Limited t/a Dragonair | ICAO: HDA, Callsign: Dragon, IATA Prefix: 043, ICAO callsign changed from Dragonair. Name changed to Hong Kong Dragon Airlines Limited t/a Cathay Dragon. | HK | AVCODES |
| 63 | KA | Airbusiness A/S | ICAO: ABZ, Callsign: Airbiz, | DK | AVCODES |
| 64 | KA | Hong Kong Dragon Airlines Limited t/a Cathay Dragon | ICAO: HDA, Callsign: Dragon, IATA Prefix: 043, Founded on 24 May 1985. Commenced operations in July 1985. Ceased operations on 21 October 2020. ICAO callsign changed from Dragonair . Name changed from Hong Kong Dragon Airlines Limited t/a Dragonair. | HK | AVCODES |
| 65 | KA | Aero Nomad Airlines, LLC | ICAO: ANK, Callsign: Aero Nomad, | KS | AVCODES |
| 66 | KA | Franz Kassecker GmbH | | DE | VKM |
| 67 | KAA | Asia Aero Survey And Consulting Engineers, Inc. | Callsign: Aasco, | ROK | AVCODES |
| 68 | KAA | Asia Aero Survey and Consulting Engineers | | | ICAO1 |
| 69 | KAABS | Kaabs Nordic AB | | SE | VKM |
| 70 | KAAD | KANADA CARRIERS | | | SCAC3 |
| 71 | KAAK | KAAKE TRUCKING COMPANY | | | SCAC3 |
| 72 | KAAL | KAALBYE SHIPPING UKRAINE | | | SCAC4 |
| 73 | KAAN | K A TRUCKING COMPANY | | | SCAC3 |
| 74 | KAAN | KRUSNIAK, ANTHONY | | | SCAC4 |
| 75 | KAAQ | KLECKER AND ANDERSON | | | SCAC3 |
| 76 | KAAR | KALITTA AIR LLC | | | SCAC4 |
| 77 | KAB | Aviabaltika | Callsign: Aviabaltika, | LT | AVCODES |
| 78 | KAB | Air Pohang Co., Ltd. | IATA: RN, Callsign: Air Pohang, Commenced operations on 07 February 2018. Ceased operations on 29 November 2018. | ROK | AVCODES |
| 79 | KABA | K A BAIT LTD | | | SCAC4 |
| 80 | KABB | KAB-8 INC | | | SCAC4 |
| 81 | KABD | KAIBAB DISTRIBUTION CORPOORTATION | | | SCAC3 |
| 82 | KABG | KAMLOOPS AUGERING & BORING LTD | | | SCAC4 |
| 83 | KABH | KALBACH, C H TRUCKING | | | SCAC3 |
| 84 | KABI | KAIBAB TRANSPORTATION INC | | | SCAC3 |
| 85 | KABI | KABAILCO INC | | | SCAC4 |
| 86 | KABL | KABLE BROTHERS TRANSPORT | | | SCAC3 |
| 87 | KABM | KORTSCH, A B C MOVING & STORAGE INC | | | SCAC3 |
| 88 | KABM | KAPA LOGISTICS LTD | | | SCAC4 |
| 89 | KABO | KABECO INC | | | SCAC3 |
| 90 | KABO | KAILE7 TRANSPORT INC | | | SCAC4 |
| 91 | KABQ | KABBES TURCKING | | | SCAC3 |
| 92 | KABQ | KCLA TRANSPORTATION | | | SCAC4 |
| 93 | KABR | K AND B TRANSPORTATION LLC | | | SCAC4 |
| 94 | KABX | Canadian Resource Distribution Inc. | 7/2000-7/2005 (not listed) | | NAKINA |
| 95 | KABX | Kaber Co. | 1/1994 (not listed) | | NAKINA |
| 96 | KABX | Bay State Milling Co. | eliminated 10/1993 | | NAKINA |
| 97 | KABX | Kaber Co. | 1/1975; added 4/1975; 1/1980; eliminated 7/1993 | | NAKINA |
| 98 | KABX | Kaber Co. | 1/75; added 4/75; 1/80; eliminated 7/93 | | NRHS |
| 99 | KABX | Bay State Milling Co. | eliminated 10/93 | | NRHS |
| 100 | KABX | Kaber Co. | Jan-94 | | NRHS |
