| 1 | MK | Air Mauritius | ICAO: MAU, Callsign: Airmauritius, IATA Prefix: 239, | MUS | AVCODES |
| 2 | MK&T | Missouri, Kansas & Texas Ry. (M. K. & T. Lines) | 8/1920 | | NAKINA |
| 3 | MK&T | UNION PACIFIC RAILROAD CO. [MISSOURI PACIFIC; MISSOURI, KANSAS & TEXAS RWY.; M.K. & T. LINES] | | | PWRC |
| 4 | MKA | MK Airlines Limited | IATA: 7G, Callsign: Kruger-Air, IATA Prefix: 513, Registered country changed from Ghana | GB | AVCODES |
| 5 | MKA | MK Airlines Limited | IATA: 7G, Callsign: Kruger-Air, IATA Prefix: 513, Registered country changed to United Kingdom | GH | AVCODES |
| 6 | MKA | MK Airlines Limited | Callsign: Kruger-Air, IATA Prefix: 513, Ceased Operation. Voluntarily surrendered AOC 09 April 2010. Registered country changed from Ghana | GB | AVCODES |
| 7 | MKA | Moka Airways | Callsign: Moka Air, | YAR | AVCODES |
| 8 | MKA | MK Airline | | | ICAO1 |
| 9 | MKAA | MCKANN TRANSPORT LLC | | | SCAC4 |
| 10 | MKAB | MACKS FARM & RV CENTER | | | SCAC4 |
| 11 | MKAD | MC KINNIE TRUCKING LLC | | | SCAC4 |
| 12 | MKAG | MILLER LIVESTOCK INC | | | SCAC4 |
| 13 | MKAJ | MORRIS KREITZ AND SON INC | | | SCAC4 |
| 14 | MKAK | MIKES AUTO TRANSPORT LLC | | | SCAC4 |
| 15 | MKAT | MACKAT INC | | | SCAC4 |
| 16 | MKAT | Przedsiębiorstwo Komunikacji Miejskiej Katowice | | PL | TRAFFIC |
| 17 | MKAU | RWE NUCLEAR GMBH | | D | BIC |
| 18 | MKAV | MKAT SERVICES LLC | | | SCAC4 |
| 19 | MKAW | MIKES AUTO TRANSPORT | | | SCAC4 |
| 20 | MKB | Mack Air | Callsign: Greentail, | BW | AVCODES |
| 21 | MKB | AG Märkische Kleinbahn e.V. | Berlin | D | privat-bahn.de |
| 22 | MKB | Mindener Kreisbahnen GmbH | Minden | D | privat-bahn.de |
| 23 | MKB | Mindener Kreisbahnen GmbH | | D | TRAFFIC |
| 24 | MKB | Mindener Kreisbahnen | | DE | VKM |
| 25 | MKBB | MK TRANSPORT INC | | | SCAC4 |
| 26 | MKBK | MINN-KAN BROKERAGE INC | | | SCAC4 |
| 27 | MKC | Mak-Air | | MK | AVCODES |
| 28 | MKC | McKeesport Connecting R.R. Co. | 1/1946-7/2005 | | NAKINA |
| 29 | MKC | McKeesport Connecting R.R. Co. | 1/52-7/2000 | | NRHS |
| 30 | MKC | MCKEESPORT CONNECTING RAILROAD CO. | | | PWRC |
| 31 | MKC | McKeesport Connecting Railroad | | | RSRV |
| 32 | MKCB | MUELLER TRUCKING COMPANY | | | SCAC4 |
| 33 | MKCE | MKC ENTERPRISES INC | | | SCAC4 |
| 34 | MKCG | MAK CARRIERS INC | | | SCAC4 |
| 35 | MKCH | MK CARTAGE LTD | | | SCAC4 |
| 36 | MKCL | MAVRAK COMPANY LLC | | | SCAC4 |
| 37 | MKCO | MORRISON KNUDSEN CORPORATION | | | PWRC |
| 38 | MKCO | M K TRUCKING INC | | | SCAC4 |
| 39 | MKCS | MILWAUKEE-KANSAS CITY S. JOINT AGENCY | | | PWRC |
| 40 | MKCS | MUNKITTRICK TRANSPORT INC | | | SCAC4 |
| 41 | MKCT | MAESTRA LINE TRUCKING | | | SCAC4 |
| 42 | MKCX | Morrison Knudsen Corp. | 7/2000-7/2005 (not listed) | | NAKINA |
| 43 | MKCX | Michigan Chemical Co. | 7/1923 | | NAKINA |
| 44 | MKCX | Morrison Knudsen Corp. | Jul-00 | | NRHS |
| 45 | MKCX | *MICHIGAN CHEMICAL CO. | | | PWRC |
| 46 | MKCX | +MORRISON KNUDSEN CORPORATION | | | PWRC |
| 47 | MKCX | Morrison Knudsen Corporation | | | RSRV |
| 48 | MKCX | MORRISON KNUDSEN CORPORATION | | | SCAC4 |
| 49 | MKCY | MACKENZIE | | | SCAC4 |
| 50 | MKD | Mat Airways | Callsign: Matairways, Founded in March 2009. Ceased operations in 2011. | MK | AVCODES |
| 51 | MKD | MAT Airways | Real: MKD, 6F | MK | TRAFFIC |
| 52 | MKDA | MEEKER, DAVE AUTO INC | | | SCAC4 |
| 53 | MKDG | MAKUR DESIGNS INC | | | SCAC4 |
| 54 | MKDI | MEK TRUCKING | | | SCAC4 |
| 55 | MKDN | MCKAY, DON TRUCKING LIMITED | | | SCAC4 |
| 56 | MKDR | MARKDA | | | SCAC4 |
| 57 | MKDS | MIKADE DELIVERY SERVICE INC | | | SCAC4 |
| 58 | MKDT | MKD INTERNATIONAL INC | | | SCAC4 |
| 59 | MKE | PT. Megantara Air | IATA: 9M, Callsign: Megantara, IATA Prefix: 824, Founded in 2007. Ceased operations in May 2009. Designator reinstated by IATA. | RI | AVCODES |
| 60 | MKEA | MEIKLE AUTOMATION INC | | | SCAC4 |
| 61 | MKEB | MCKEE BROTHERS OIL CORP | | | SCAC4 |
| 62 | MKEC | MIKEN CARTAGE INC | | | SCAC4 |
| 63 | MKED | MACKINNON, E D TRUCKING LTD | | | SCAC4 |
| 64 | MKEE | MAKSTEE | | | SCAC4 |
| 65 | MKEI | MARKETEC TRANSPORT INCORPORATED | | | SCAC4 |
| 66 | MKEP | MALKE ENTERPRISES LTD | | | SCAC4 |
| 67 | MKER | MIDKNIGHT EXPRESS INC | | | SCAC4 |
| 68 | MKERT | MÁV KERT Kft. | | HU | VKM |
| 69 | MKES | MIKES INC | | | SCAC4 |
| 70 | MKET | MARKET TRANSPORT, LTD | | | SCAC1 |
| 71 | MKFB | MAR-KO FREIGHT SERVICES | | | SCAC4 |
| 72 | MKFC | MEAKIN FOREST ENTERPRISES INC | | | SCAC4 |
| 73 | MKFM | MCKEE FARM TECHNOLOGIES INC | | | SCAC4 |
| 74 | MKFN | MAKS FREIGHT INC | | | SCAC4 |
| 75 | MKFP | MIDKIFF COOP | | | SCAC4 |
| 76 | MKFQ | MK FREIGHT BROKER INC | | | SCAC4 |
| 77 | MKFX | Century Rail Enterprises, Inc. | 7/2005 (not listed) | | NAKINA |
| 78 | MKFX | CENTURY RAIL ENTERPRISES, INC. | | | PWRC |
| 79 | MKFX | Century Rail Enterprises | | | RSRV |
| 80 | MKG | Mekong Aviation JSC (Air Mekong) | IATA: P8, Callsign: Air Mekong, IATA Prefix: 819, Ceased operations on 01 March 2013. AOC revoked January 2015. ICAO callsign changed from Mekong | VN | AVCODES |
| 81 | MKG | Mekong Aviation JSC (Air Mekong) | IATA: P8, Callsign: Mekong, IATA Prefix: 819, ICAO callsign changed to Air Mekong | VN | AVCODES |
| 82 | MKGA | MK GAS CO | | | SCAC4 |
| 83 | MKGB | MAVERICK TRUCKING INC | | | SCAC4 |
| 84 | MKGE | MUSICK TRUCKING CO | | | SCAC4 |
| 85 | MKGF | MAK LOGISTICS LLC | | | SCAC4 |
| 86 | MKGH | MINERAL KING TRANSPORTATION LLC | | | SCAC4 |
| 87 | MKGL | MCCLAIN, TIM TRUCKING | | | SCAC4 |
| 88 | MKGM | M A C TRUCKING LTD | | | SCAC4 |
| 89 | MKGN | MIKES GLASS & MIRROR CO INC | | | SCAC4 |
| 90 | MKGO | MIMI TRUCKING LLC | | | SCAC4 |
| 91 | MKGS | MARKET LOGISTICS (DIV OF MARKET TRA | | | SCAC4 |
| 92 | MKGU | GATI COAT TO COAST | | | SCAC4 |
| 93 | MKGV | M A S TRUCKING SERVICES CORP | | | SCAC4 |
| 94 | MKGX | North American Car Corp. | added 10/1960; 4/1961-1/1975; eliminated 10/1979 | | NAKINA |
| 95 | MKGX | North American Car Corp. | added 10/60; 4/61-1/75 | | NRHS |
| 96 | MKGX | NORTH AMERICAN CAR CORP. | | | PWRC |
| 97 | MKH | Air Marrakech Service | Callsign: Air Marrakech, | MA | AVCODES |
| 98 | MKH | Air Marrakech Service | | | ICAO1 |
| 99 | MKHC | MKH TRANSPORTATION INC | | | SCAC4 |
| 100 | MKHI | MIKASHA INC | | | SCAC4 |
