| 1 | MID | Midland Airport Services | | GB | AVCODES |
| 2 | 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 |
| 3 | MID | Waters-Aero Marine, Inc. | Callsign: Midcoast, | USA | AVCODES |
| 4 | MID | Midland Airport Services | | | ICAO1 |
| 5 | MID | Midway | 1/1980 | | NAKINA |
| 6 | MID | Midway R.R. Co. | 1/1975 | | NAKINA |
| 7 | MID | Midway R.R. Co. | Jan-75 | | NRHS |
| 8 | MID | Midway | Jan-80 | | NRHS |
| 9 | MID | MIDWAY RAILROAD CO. | | | PWRC |
| 10 | MID | Midway Railroad | | | RSRV |
| 11 | MID | MID-TENN TOURS | | | SCAC4 |
| 12 | 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 |
| 13 | MIDC | *MID CONTINENT FREIGHT LINES | | | PWRC |
| 14 | MIDC | *MIDLAND CONTINENTAL RAILROAD | | | PWRC |
| 15 | MIDC | MID COUNTIES DELIVERY SERVICE, INC | | | SCAC1 |
| 16 | MIDC | MidCargo AB | | SE | VKM |
| 17 | MIDD | MID STATE TRANSPORT LLC | | | SCAC4 |
| 18 | MIDF | MIDWEST GLOBAL INC | | | SCAC4 |
| 19 | MIDG | MID AMERICA OVERSEAS (SHANGHAI) LTD | | | SCAC4 |
| 20 | MIDH | Middletown & Hummelstown R.R. Co. | 1/1980-7/2005 | | NAKINA |
| 21 | MIDH | Middletown & Hummelstown R.R. Co. | 1/80-7/2000 | | NRHS |
| 22 | MIDH | MIDDLETOWN & HUMMELSTOWN RAILROAD CO. | | | PWRC |
| 23 | MIDH | Middletown and Hummelstown Railroad | | | RSRV |
| 24 | MIDH | Middletown and Hummelstown Railroad | | USA | TRAFFIC |
| 25 | MIDI | Compagnie des chemins de fer du Midi | | F | TRAFFIC |
| 26 | MIDK | MIDI LOGISTICS INC | | | SCAC4 |
| 27 | MIDL | MIDLAND RAILWAY | | | PWRC |
| 28 | MIDL | Midland Railway | | | RSRV |
| 29 | MIDL | MOUNTAIN INTERMODAL INC | | | SCAC4 |
| 30 | MIDQ | MIDWEST QUALITY TRANSPORT LTD | | | SCAC4 |
| 31 | MIDU | MIDGAS FOR INDUSTRIAL GASES | | ET | BIC |
| 32 | MIDV | MID MICHIGAN MOVING & STORAGE | | | SCAC4 |
| 33 | MIDW | MIDWEST MOTOR EXPRESS INC | | | PWRC |
| 34 | MIDW | MIDWEST MOTOR EXPRESS, INC | | | SCAC1 |
| 35 | MIDW | MIDWEST MOTOR EXPRESS INC | | | SCAC4 |
| 36 | MIDW | Mid Warwickshire | | GB | TRAFFIC |
| 37 | MIDX | Mitsui Rail Capital, LLG | 7/2005, eliminated 1/2010 | | NAKINA |
| 38 | MIDX | MRC Rail Services, LLC | added 4/1998; 7/2000 | | NAKINA |
| 39 | MIDX | Unitrain, Inc. | added 1/1994; eliminated 4/1998 | | NAKINA |
| 40 | MIDX | Midwest Energy Services Co. | added 4/1989; 1/1994 | | NAKINA |
| 41 | MIDX | Merchants Despatch Transportation Co. | added 10/1962; 7/1965-4/1970; eliminated 1/1973 | | NAKINA |
| 42 | MIDX | Midland Packing Co. | 8/1920 | | NAKINA |
| 43 | MIDX | Merchants Despatch Transportation Co. | 7/65-4/70; eliminated 1/73 | | NRHS |
| 44 | MIDX | Midwest Energy Services Co. | added 4/89; 1/94 | | NRHS |
| 45 | MIDX | Unitrain, Inc. | added 1/94; eliminated 4/98 | | NRHS |
| 46 | MIDX | MRC Rail Services, LLC | added 4/98; 7/2000 | | NRHS |
| 47 | MIDX | *MIDLAND PACKING CO. | | | PWRC |
| 48 | MIDX | *MERCHANTS DESPATCH TRANSPORTATION CO. | | | PWRC |
| 49 | MIDX | +MITSUI RAIL CAPITAL, LLC [MRC RAIL SERVICES LLP ; UNITRAIN, INC.; MIDWEST ENERGY SERVICES] | | | PWRC |
| 50 | MIDX | MRC Rail Services | | | RSRV |
| 51 | MIDX | Middlesex Bus Company | | US-NJ | TRAFFIC |
| 52 | MIDY | MIDDLEMAN INSTALLATION & DELIVERY I | | | SCAC4 |
| 53 | MIDZ | MID CITIES MOTOR FREIGHT INC | | | SCAC4 |
