| 1 | MI | SilkAir (S) Pte. Ltd. | ICAO: SLK, Callsign: Silkair, IATA Prefix: 629, Name changed to SilkAir (SINGAPORE) Pte. Ltd. | SGP | AVCODES |
| 2 | MI | Mackey International | Callsign: Mackey, | USA | AVCODES |
| 3 | MI | Freebird Airlines Europe Limited | ICAO: FHM, Callsign: Eurobird, | M | AVCODES |
| 4 | MI | SilkAir (SINGAPORE) Pte. Ltd. | ICAO: SLK, Callsign: Silkair, IATA Prefix: 629, Merged into Singapore Airlines. Name changed from SilkAir (S) Pte. Ltd. | SGP | AVCODES |
| 5 | MI | Union Pacific R.R. Co. | added 4/1997; 7/2000-7/2005 | | NAKINA |
| 6 | MI | Missouri Pacific System | 1/1994; eliminated 4/1997 | | NAKINA |
| 7 | MI | Missouri Pacific R.R. Co. | 1/1980 | | NAKINA |
| 8 | MI | Missouri-Illinois R.R. Co. | 10/1957-10/1966 & 1/1975 | | NAKINA |
| 9 | MI | Minnesota & International Ry. Co. | 4/1938-1/1941 | | NAKINA |
| 10 | MI | Minnesota & International Ry. Co. | Apr-38 | | NRHS |
| 11 | MI | Missouri-Illinois R.R. Co. | 10/57-10/66 & 1/75 | | NRHS |
| 12 | MI | Missouri Pacific R.R. Co. | Jan-80 | | NRHS |
| 13 | MI | Missouri Pacific System | 1/94; eliminated 4/97 | | NRHS |
| 14 | MI | Union Pacific R.R. Co. | added 4/97; 7/2000 | | NRHS |
| 15 | MI | *MINNESOTA & INTERNATIONAL RWY. CO. | | | PWRC |
| 16 | MI | +UP [MISSOURI PACIFIC; MISSOURI - ILLINOIS RR.] | | | PWRC |
| 17 | MI | Missouri-Illinois Railroad (Union Pacific Railroad) | | | RSRV |
| 18 | MI | Missouri-Illinois R.R. Co. | | USA | TRAFFIC |
| 19 | MIA | Mauria, Société Mauritanienne D'aviation | Callsign: Mauria, | RIM | AVCODES |
| 20 | MIA | Mauria | | | ICAO1 |
| 21 | MIA | MID-AMERICAN COACHES INC | | | SCAC4 |
| 22 | MIAB | MARLEON INTERNATIONAL LLC | | | SCAC4 |
| 23 | MIAC | MIAMI CRATING CO | | | SCAC4 |
| 24 | MIAJ | MIOARAS ORIGINAL SILK | | | SCAC4 |
| 25 | MIAL | MINUTEMAN POWERBOSS | | | SCAC4 |
| 26 | MIAM | MIAMI TRANSPORT INCORPORATED | | | SCAC4 |
| 27 | MIAO | MITCHELL CONCESSIONS LTD | | | SCAC4 |
| 28 | MIAQ | MID ATLANTIC PORT SERVICE | | | SCAC4 |
| 29 | MIAR | MIDNIGHT OIL COMPANY | | | SCAC4 |
| 30 | MIAU | MONTEBELLO AG | | CH | BIC |
| 31 | MIAY | MIDWEST INSURANCE AGENCY INC | | | SCAC4 |
| 32 | MIB | Meiringen-Innertkirchen-Bahn/Kraftwerk Oberhasli | Real: MIB/KWO, 5km narrow gauge(1000mm), electrified at 1200V= This line used to be a construction railway for the hydro-electric power plant. Later the line was opened to the public and operated by battery cars. In 1977 it was electrified and second-hand cars were bought from OEG in Mannheim(D). | CH | TRAFFIC |
| 33 | MIB | Kraftwerk Oberhasli (Meiringen-Innertkirchen-Bahn) | | CH | VKM |
| 34 | MIBA | MACTRAN INC | | | SCAC4 |
| 35 | MIBF | MD INTERNATIONAL BAJA S DE RL | | | SCAC4 |
| 36 | MIBG | MACHINECRAFT INC | | | SCAC4 |
| 37 | MIBI | MITSUBISHI ORE TRANSPORT CO LTD | | | SCAC4 |
| 38 | MIBL | MILLENNIUM TRUCKING INC | | | SCAC4 |
| 39 | MIBM | MOVE-IT-BROKERAGE LLC | | | SCAC4 |
| 40 | MIBP | MONTICELLO FLOORING & LUMBER CO INC | | | SCAC4 |
| 41 | MIBQ | MAYTRANS INTERNATIONAL CORP | | | SCAC4 |
| 42 | MIBR | MILLER BROS | | | SCAC1 |
| 43 | MIBR | M I B TRUCKING INC | | | SCAC4 |
| 44 | MIBRAG | Mitteldeutsche Braunkohle AG | | D | TRAFFIC |
| 45 | MIC | Aerolineas de Michoacan | Callsign: Michoacan, | MEX | AVCODES |
| 46 | MIC | Mint Lineas Aereas, S.L. | IATA: IM, Callsign: Mint Airways, Founded in 2009. Ceased operations on 22 May 2012. | E | AVCODES |
| 47 | MIC | Michels GmbH & Co. KG | | DE | VKM |
| 48 | MICB | MID CITIES MOTOR FREIGHT INC | | | SCAC4 |
| 49 | MICC | MALPICA EXPRESS SA DE CV | | | SCAC4 |
| 50 | MICD | MICHIGAN CARPET DELIVERY | | | SCAC4 |
| 51 | MICE | MID-IOWA COOPERATIVE | | | SCAC4 |
| 52 | MICH | MICHELIN AMERICAS RESEARCH COMPANY | | | SCAC4 |
| 53 | MICHA | Michalczewski Sp. z o.o. | City: Radom | PL | TRAFFIC |
| 54 | MICI | MINIC INDUSTRIES LIMITED | | | SCAC4 |
| 55 | MICK | MICKY TRANSPORT LTD | | | SCAC4 |
| 56 | MICM | MINCHEM INTERNATIONAL INC | | | SCAC4 |
| 57 | MICN | MEDINA LODI INC | | | SCAC4 |
| 58 | MICO | Midland Continental R.R. | 10/1966 | | NAKINA |
| 59 | MICO | Midland Continental R.R. | Oct-66 | | NRHS |
| 60 | MICO | MIDLAND CONTINENTAL RAILROAD | | | PWRC |
| 61 | MICO | MITSUI & CO LTD | | | SCAC4 |
| 62 | MICP | MISSOURI GAS ENERGY | | | SCAC4 |
| 63 | MICR | MICHIGAN CENTRAL RAILROAD CO. | | | PWRC |
| 64 | MICT | MICHIGAN CARTAGE MI-CART INC | | | SCAC4 |
| 65 | MICU | PAN PACIFIC INTL TRADING GROUP (HK) LTD | | HK | BIC |
| 66 | MICW | MCS INTERNATIONAL MARINE SERVICES B | | | SCAC4 |
| 67 | MICX | Mississippi Chemical Corp. | added 10/1972; 1/1975-1/1980; eliminated 10/1981 | | NAKINA |
| 68 | MICX | Mis Coa, a partnership of Mississippi Chemical Corp. and Coastal Chemical Corp. | added 7/1971; eliminated 10/1972 | | NAKINA |
| 69 | MICX | Mississippi Chemical Corp. | 1/1952-4/1970; eliminated 7/1971 | | NAKINA |
| 70 | MICX | Mid-Continent Refining Co. | 8/1920-7/1923 | | NAKINA |
| 71 | MICX | Mis Coa, a partnership of Mississippi Chemical Corp. and Coastal Chemical Corp. | eliminated 10/72 | | NRHS |
| 72 | MICX | Mississippi Chemical Corp. | 1/52-4/70 | | NRHS |
| 73 | MICX | Mississippi Chemical Corp. | added 10/72; 1/75-1/80; eliminated 10/81 | | NRHS |
| 74 | MICX | *MID-CONTINENT REFINING CO. | | | PWRC |
| 75 | MICX | *MISSISSIPPI CHEMICAL CO. [MIS COA] | | | PWRC |
| 76 | MICX | CANCELLED ID - FORMERLY A RAILINC TCAM ID | | | PWRC |
| 77 | MICZ | MID IOWA COOP | | | PWRC |
| 78 | MID | Midland Airport Services | | GB | AVCODES |
| 79 | MID | Midway Airlines | IATA: ML, Callsign: Midway, Founded on 06 August 1976. Filed for Chapter 11 bankruptcy portection March 1991. Ceased operations on 13 November 1991. | USA | AVCODES |
| 80 | MID | Waters-Aero Marine, Inc. | Callsign: Midcoast, | USA | AVCODES |
| 81 | MID | Midland Airport Services | | | ICAO1 |
| 82 | MID | Midway | 1/1980 | | NAKINA |
| 83 | MID | Midway R.R. Co. | 1/1975 | | NAKINA |
| 84 | MID | Midway R.R. Co. | Jan-75 | | NRHS |
| 85 | MID | Midway | Jan-80 | | NRHS |
| 86 | MID | MIDWAY RAILROAD CO. | | | PWRC |
| 87 | MID | Midway Railroad | | | RSRV |
| 88 | MID | MID-TENN TOURS | | | SCAC4 |
| 89 | MID | Midland Main Line Ltd. | Real: MML, 1999: 477km standard gauge, not electrified. Midland Mainline (MML) is a British train operating company, created after the privatisation of British Rail. It runs passenger services from London St Pancras to the East Midlands and Yorkshire, on the Midland Main Line. MML is based in Derby and owned by the National Express Group. | GB | TRAFFIC |
| 90 | MIDC | *MID CONTINENT FREIGHT LINES | | | PWRC |
| 91 | MIDC | *MIDLAND CONTINENTAL RAILROAD | | | PWRC |
| 92 | MIDC | MID COUNTIES DELIVERY SERVICE, INC | | | SCAC1 |
| 93 | MIDC | MidCargo AB | | SE | VKM |
| 94 | MIDD | MID STATE TRANSPORT LLC | | | SCAC4 |
| 95 | MIDF | MIDWEST GLOBAL INC | | | SCAC4 |
| 96 | MIDG | MID AMERICA OVERSEAS (SHANGHAI) LTD | | | SCAC4 |
| 97 | MIDH | Middletown & Hummelstown R.R. Co. | 1/1980-7/2005 | | NAKINA |
| 98 | MIDH | Middletown & Hummelstown R.R. Co. | 1/80-7/2000 | | NRHS |
| 99 | MIDH | MIDDLETOWN & HUMMELSTOWN RAILROAD CO. | | | PWRC |
| 100 | MIDH | Middletown and Hummelstown Railroad | | | RSRV |
