| 4201 | MISR | MILLER TRUCK & STORAGE COMPANY | | | SCAC4 |
| 4202 | MISS | The Mississippian Ry. Cooperative, Inc. | added 1/1987; 1/1994-7/2005 | | NAKINA |
| 4203 | MISS | The Mississippian Ry., Inc. | added 1/1981; eliminated 1/1987 | | NAKINA |
| 4204 | MISS | Mississippian | 1/1975-1/1980 | | NAKINA |
| 4205 | MISS | Mississippian | 1/75-1/80 | | NRHS |
| 4206 | MISS | The Mississippian Ry., Inc. | added 1/81; eliminated 1/87 | | NRHS |
| 4207 | MISS | The Mississippian Ry. Cooperative, Inc. | added 1/87; 1/94-7/2000 | | NRHS |
| 4208 | MISS | (MSRW) MISSISSIPPIAN RAILWAY COOPERATIVE, INC. | | | PWRC |
| 4209 | MISS | Mississippian Railway Cooperative | | | RSRV |
| 4210 | MISS | MISSISSIPPI | | | SCAC4 |
| 4211 | MISS | Mississauga Transit | City: Mississauga | CDN | TRAFFIC |
| 4212 | MIST | MERRILL IRON & STEEL SERVICES LLC | | | SCAC4 |
| 4213 | MISU | MIOULIO SHIPPING COMPANY LIMITED | | CY | BIC |
| 4214 | MISU | MALAYSIAN INTERNATIONAL SHIPPING CORP. | | | PWRC |
| 4215 | MISU | Malaysian International Shipping Corporation | | | RSRV |
| 4216 | MISU | MALAYSIAN INTL SHIPPING CORPORATION | | | SCAC4 |
| 4217 | MISX | Milwaukee Solvents & Chemicals Corp. | added 1/1974; 1/1975-1/1994; 7/2000 (not listed) | | NAKINA |
| 4218 | MISX | Milwaukee Solvents & Chemicals Corp. | added 1/74; 1/75-7/2000 | | NRHS |
| 4219 | MISX | MILWAUKEE SOLVENTS & CHEMICALS CORP. | | | PWRC |
| 4220 | MISX | Milwaukee Solvents and Chemicals Corporation | | | RSRV |
| 4221 | MISX | MI LLC | | | SCAC4 |
| 4222 | MISY | MILLS INDUSTRIAL SUPPLY 1996 LTD | | | SCAC4 |
| 4223 | MIT | Flight Line, Inc. | Callsign: Matco, | USA | AVCODES |
| 4224 | MIT | Flight Line | | | ICAO1 |
| 4225 | MITA | MITCHEK, ALLEN | | | SCAC4 |
| 4226 | MITB | M & I TRANSPORTATION INC | | | SCAC4 |
| 4227 | MITB | Mitcham Belle | | GB | TRAFFIC |
| 4228 | MITC | MISSION TRANSPORT COMPANY | | | SCAC4 |
| 4229 | MITH | MITCHELL BROS TRUCK LINE INC | | | SCAC4 |
| 4230 | MITI | MARKET TRANSPORT SERVICES - INTRANS | | | SCAC4 |
| 4231 | MITK | MITKO & KAPRI TRUCKING INC | | | SCAC4 |
| 4232 | MITL | MIDWEST TRANSPORT LOGISTICS LLC | | | SCAC4 |
| 4233 | MITL | Majestic Imperator Train de Luxe Waggon Charter GmbH | | AT | VKM |
| 4234 | MITM | MICHIGAN TRANSIT MUSEUM | | | PWRC |
| 4235 | MITN | MILLER TRANSPORTERS INC | | | SCAC4 |
| 4236 | MITO | MILLER TRUCKING CORPORATION | | | SCAC4 |
| 4237 | MITP | M I TRANSPORT | | | SCAC4 |
| 4238 | MITR | M I T RENTAL LLC | | | SCAC4 |
| 4239 | MITR | Mitropa | | D | TRAFFIC |
| 4240 | MITRA | Mitrag AG | | CH | VKM |
| 4241 | MITRAG | Mitrag AG | | CH | TRAFFIC |
| 4242 | MITS | MITSUI STEAMSHIP CO | | | PWRC |
| 4243 | MITS | Mitshubishi | | J | TRAFFIC |
| 4244 | MITSUI | Mitsui Mining Co., Ltd. | | J | TRAFFIC |
| 4245 | MITTENWALD | Mittenwaldbahn | | A | TRAFFIC |
| 4246 | MITU | PS SURVEY & CLAIM SERVICES APS | | DK | BIC |
| 4247 | MITV | MAGNUM INTERNATIONAL TRANSPORTATION | | | SCAC4 |
| 4248 | MITX | Interall Holdings, Inc. | added 10/1960; 4/1961; eliminated 4/1963 | | NAKINA |
| 4249 | MITX | Interall Holdings, Inc. | added 10/60; 4/61 | | NRHS |
| 4250 | MITX | INTERALL HOLDINGS, INC. | | | PWRC |
| 4251 | MIUK | MITSUI-SOKO (U S A) INCORPORATED | | | SCAC4 |
| 4252 | MIUL | M&I TRUCK LINE, INC | | | SCAC1 |
| 4253 | MIV | Mi-avia | Callsign: Miavia, | RUS | AVCODES |
| 4254 | MIVR | MCIVER TRANSPORT | | | SCAC4 |
| 4255 | MIVRTA | Miami Valley Regional Transit Authority | City: Dayton OH | USA | TRAFFIC |
| 4256 | MIVT | MARK FOUR (IV) TRANSPORTATION CO IN | | | SCAC4 |
| 4257 | MIW | Airborne of Sweden AB | IATA: ZF, Callsign: Midwing, Designator ZF recalled by IATA | S | AVCODES |
| 4258 | MIW | Tomahawk Ry., Limited Partnership | eliminated 4/1995 | | NAKINA |
| 4259 | MIW | Tomahawk Ry., Limited Partnership | eliminated 4/95 | | NRHS |
| 4260 | MIW | TOMOHAWK RWY., LP | | | PWRC |
| 4261 | MIWC | MIDWEST CARPET CARRIERS | | | SCAC4 |
| 4262 | MIWD | MILLWOOD TRUCKING INC | | | SCAC4 |
| 4263 | MIWI | MGP INGREDIENTS INC | | | SCAC4 |
| 4264 | MIWL | MIAMI WELDING | | | SCAC4 |
| 4265 | MIWY | MIDWAY | | | SCAC4 |
| 4266 | MIX | Masisavia | Callsign: Masis, | AM | AVCODES |
| 4267 | MIX | Midex Airlines | IATA: MG, Callsign: Midexcargo, IATA Prefix: 791, | UAE | AVCODES |
| 4268 | MIX | Milton Ice Co., Inc. | 7/1935 | | NAKINA |
| 4269 | MIXB | MIDNIGHT XPRESS | | | SCAC4 |
| 4270 | MIXC | MIDTRANS INC | | | SCAC4 |
| 4271 | MIXD | MIDNIGHT EXPRESS & CARTAGE LTD | | | SCAC4 |
| 4272 | MIXE | MICHIGAN EXPRESS INC | | | PWRC |
| 4273 | MIXH | MEADE INSTRUMENTS | | | SCAC4 |
| 4274 | MIXK | MATRIX TRUCKING | | | SCAC4 |
| 4275 | MIXO | MIXSON OIL CO INC | | | SCAC4 |
| 4276 | MIXP | MILAN EXPRESS LTD | | | SCAC4 |
| 4277 | MIXQ | MANHATTAN INTERNATIONAL TRANSPORTAT | | | SCAC4 |
| 4278 | MIXR | MCMURRY READY MIX CO | | | SCAC4 |
| 4279 | MIXT | MIX TRUCKING | | | SCAC4 |
| 4280 | MIXU | LOGISTICA SUARDIAZ SL | | E | BIC |
| 4281 | MIXU | VAPORES SUARDIAZ S A | | | SCAC4 |
| 4282 | MIYA | MINATOYA CORPORATION | | | SCAC4 |
| 4283 | MIYAGI | Miyagi Electric Railway | Predecessor of the Senseki line | J | TRAFFIC |
| 4284 | MIYAGO | Miyago Bus | | J | TRAFFIC |
| 4285 | MIYAKO | Miyazaki Kotsu Co. Ltd. | | J | TRAFFIC |
| 4286 | MIZ | Desarrollo Milaz, S.A. de C.V. | Callsign: Milaz, | MEX | AVCODES |
| 4287 | MIZ | Desarrollo Milaz | | | ICAO1 |
| 4288 | MIZ | MENDERHALL, INC. | | | PWRC |
| 4289 | MIZR | MIZAR MOTORS INC | | | SCAC4 |
| 4290 | MIZURIN | Mizushima Rinkai Railway Co., Ltd. | | J | TRAFFIC |
| 4291 | MJ | Lineas Aereas Privadas Argentinas (LAPA) | ICAO: LPR, Callsign: Lapa, IATA Prefix: 069, Name changed to ARG L�nea Privada Argentina on 27 September 2001. | RA | AVCODES |
| 4292 | MJ | Manchester Airport Agencies | | GB | AVCODES |
| 4293 | MJ | Mihin Lanka (Pvt) Ltd. | ICAO: MLR, Callsign: Mihin Lanka, Ceased operations on 30 October 2016. | CL | AVCODES |
| 4294 | MJ | M & N Equipment, LLC d/b/a M & N Aviation | ICAO: JNH, Callsign: Jonah, Designator MJ* recalled by IATA. | USA | AVCODES |
| 4295 | MJ | ARG Línea Privada Argentina | ICAO: LPR, Callsign: Lapa, IATA Prefix: 069, Name changed from Lineas Aereas Privadas Argentinas (LAPA) on 27 September 2001. Ceased operations in April 2003. | RA | AVCODES |
| 4296 | MJ | MyWay Airlines Co., Ltd. | ICAO: MYW, Callsign: My Sky, Commenced operations on 31 March 2018. | GE | AVCODES |
| 4297 | MJ | Manufacturers' Junction Ry. Co. | 8/1920-7/2005; eliminated 1/2006 | | NAKINA |
| 4298 | MJ | Manufacturers' Junction Ry. Co. | 4/38-7/2000 | | NRHS |
| 4299 | MJ | MANUFACTURERS JUNCTION RAILWAY CO. | | | PWRC |
| 4300 | MJ | Manufacturers' Junction Railway | | | RSRV |
