| 8301 | MSX | *MORTON SALT CO. | | | PWRC |
| 8302 | MSXC | M S TRANSPORT | | | SCAC4 |
| 8303 | MSXD | MICHAEL AND SONS EXPRESS TRANSPORT | | | SCAC4 |
| 8304 | MSXG | MOSAIC LOGISTICS | | | SCAC4 |
| 8305 | MSXH | M S TRANSPORT CO | | | SCAC4 |
| 8306 | MSXK | MOSKITO EXPRESS | | | SCAC4 |
| 8307 | MSXM | MST TRANSPORT | | | SCAC4 |
| 8308 | MSXN | MID-STATES EXPRESS, INC | | | SCAC1 |
| 8309 | MSXO | MIDLAND SIXTY-SIX OIL CO | | | SCAC4 |
| 8310 | MSXQ | MAC SPECIAL TRANSPORT LLC | | | SCAC4 |
| 8311 | MSXR | MIDDLESEX TRANSPORTATION AND MANAGE | | | SCAC4 |
| 8312 | MSXS | MARTIN ENTERPRISES INC | | | SCAC4 |
| 8313 | MSXU | MARINE SPILL RESPONSE CORPORATION, | | | SCAC4 |
| 8314 | MSXV | MSL TRANSPORTATION INC | | | SCAC4 |
| 8315 | MSXW | MTS TRANSPORT LLC | | | SCAC4 |
| 8316 | MSXY | MRS TRANSPORT | | | SCAC4 |
| 8317 | MSY | Massey University School Of Aviation | Callsign: Massey, | NZ | AVCODES |
| 8318 | MSY | Massey University School of Aviation | | | ICAO1 |
| 8319 | MSYA | MASNEY AUTO TRANSPORT INC | | | SCAC4 |
| 8320 | MSYC | MI SYSTEMS INC | | | SCAC4 |
| 8321 | MSYF | METRO RACING SYSTEMS INC | | | SCAC4 |
| 8322 | MSYH | MASSEY HAULING CO INC | | | SCAC4 |
| 8323 | MSYK | MS TRUCKING | | | SCAC4 |
| 8324 | MSYM | MC SYSTEMS INC | | | SCAC4 |
| 8325 | MSYN | MONSEY ONE INC | | | SCAC4 |
| 8326 | MSYO | MOOSE COUNTRY OUTFITTING | | | SCAC4 |
| 8327 | MSYP | MSN TRANSPORT | | | SCAC4 |
| 8328 | MSYS | MEGA SUPPLY CHAIN SOLUTIONS INC | | | SCAC4 |
| 8329 | MSYU | MSC- MEDITERRANEAN SHIPPING COMPANY S.A. | | CH | BIC |
| 8330 | MSZ | MCLOUTH STEEL | | | PWRC |
| 8331 | MSZA | MTA | | | SCAC4 |
| 8332 | MSZG | MESA LOGISTICS | | | SCAC4 |
| 8333 | MSZK | MESA TRUCKING | | | SCAC4 |
| 8334 | MSZL | MONSTER SPECIALIZED LLC | | | SCAC4 |
| 8335 | MSZP | MILLER SPECIALIZED TRANSPORT | | | SCAC4 |
| 8336 | MSZR | MORE SPECIALIZED TRANSPORT | | | SCAC4 |
| 8337 | MSZT | MORNING STAR TRUCKING LLC | | | SCAC4 |
| 8338 | MSZU | MSC- MEDITERRANEAN SHIPPING COMPANY S.A. | | CH | BIC |
| 8339 | MT | RAF-Avia | ICAO: MTL, Callsign: Mitavia, Established on 31 October 1990. Commenced operations on 19 August 1991. | LV | AVCODES |
| 8340 | MT | JMC Airlines Limited | ICAO: JMC, Callsign: JayEmmSee, Name changed to Thomas Cook Airlines U.K. Ltd. ICAO designator changed to TCX. ICAO Callsign changed to Globe. | GB | AVCODES |
| 8341 | MT | Flying Colours Airlines Limited | ICAO: FCL, Callsign: Colours, Merged into JMC on 27 March 2002. | GB | AVCODES |
| 8342 | MT | Mid Airlines | ICAO: MDZ, Designator MT recalled by IATA | ZW | AVCODES |
| 8343 | MT | Thomas Cook Airlines U.K. Ltd. | ICAO: TCX, Callsign: Globe, IATA Prefix: 092, ICAO callsign changed to Topjet. Name changed from JMC Airlines Limited. ICAO designator changed from JMC. ICAO callsign changed from JayEmmSee | GB | AVCODES |
| 8344 | MT | Mey-Air Transoport A/S | Callsign: Maritime, | N | AVCODES |
| 8345 | MT | Thomas Cook Airlines U.K. Ltd. | ICAO: TCX, Callsign: Topjet, IATA Prefix: 092, ICAO callsign changed from Globe. Name changed from JMC Airlines Limited. ICAO designator changed from JMC. ICAO callsign changed from JayEmmSee | GB | AVCODES |
| 8346 | MT | Thomas Cook Airlines Limited of Manchester | ICAO: TCX, Callsign: Kestrel, IATA Prefix: 727, ICAO callsign changed to Thomas Cook w.e.f. 01 November 2018 previously changed from Topjet. Name changed from JMC Airlines Limited. ICAO designator changed from JMC. ICAO callsign changed from JayEmmSee | GB | AVCODES |
| 8347 | MT | Thomas Cook Airlines Limited of Manchester | ICAO: TCX, Callsign: Thomas Cook, IATA Prefix: 727, Ceased operations on 28 September 2019. ICAO callsign changed from Kestral w.e.f. 01 November 2018 previously changed from Topjet. Name changed from JMC Airlines Limited. ICAO designator changed from JMC. ICAO callsign changed from JayEmmSee | GB | AVCODES |
| 8348 | MT | Malta Air Travel Ltd d/b/a Malta MedAir | ICAO: MMO, Callsign: Malit, IATA Prefix: 323, IATA designator changed from MM*. | M | AVCODES |
| 8349 | MT | Mississipppi & Tennessee RailNet, Inc. | 7/2000-7/2005 | | NAKINA |
| 8350 | MT | Mississipppi & Tennessee RailNet, Inc. | Jul-00 | | NRHS |
| 8351 | MT | MISSISSIPPI & TENNESSEE RAILNET, INC. | | | PWRC |
| 8352 | MT | Mississippi and Tennessee RailNet | | | RSRV |
| 8353 | MT | Metro de Mirandela | | E | TRAFFIC |
| 8354 | MT | METRANS, a.s. | | CZ | VKM |
| 8355 | MT&E | Morristown & Erie R.R. | 8/1920-10/1957 | | NAKINA |
| 8356 | MT&E | Morristown & Erie R.R. | 4/38-10/57 | | NRHS |
| 8357 | MT&E | MORRISTOWN & ERIE RAILROAD | | | PWRC |
| 8358 | MTA | Mitchell Aero, Inc. d/b/a Gak/Mitchell Aero, Inc. | Callsign: Gak Aviation, | USA | AVCODES |
| 8359 | MTA | GAK/Mitchell Aero | | | ICAO1 |
| 8360 | MTA | METROPOLITAN TRANSPORTATION AUTHORITY (NEW YORK) | | | PWRC |
| 8361 | MTA | Metropolitan Transport Authority | City: New York | USA | TRAFFIC |
| 8362 | MTAA | MTA TRANSPORTATION INC | | | SCAC4 |
| 8363 | MTAB | Malmtrafik AB (Malmbanen) | 1996 - | S | svenska-lok.se |
| 8364 | MTAB | Metropolitan Transport Authority Bus Company | | USA | TRAFFIC |
| 8365 | MTAB | Malmtrafik i Kiruna AB | | SE | VKM |
| 8366 | MTAC | MINATITLAN AL CARMEN RAILROAD | | | PWRC |
| 8367 | MTAC | MORGAN LOGISTICS LLC | | | SCAC4 |
| 8368 | MTAD | MILLER TRANSFER & STORAGE | | | SCAC4 |
| 8369 | MTAF | MATA TRUCKING INC | | | SCAC4 |
| 8370 | MTAI | MT TRANSPORTATION SERVICES INC | | | SCAC4 |
| 8371 | MTAK | MAICOLC TRANSPORT | | | SCAC4 |
| 8372 | MTALIB | MTA Long Island Bus | | USA | TRAFFIC |
| 8373 | MTAM | MTB FREIGHTWAYS LTD | | | SCAC4 |
| 8374 | MTAP | METAUX PRODUIT DT INC | | | SCAC4 |
| 8375 | MTAP | Metropolitan Toronto Auxiliary Police | | CDN | TRAFFIC |
| 8376 | MTAS | METRO ATLANTA EXPRESS | | | SCAC4 |
| 8377 | MTAS | | | N | TRAFFIC |
| 8378 | MTAS | Malmtrafik A/S | | NO | VKM |
| 8379 | MTAU | FINEBRO 3 S.L. | | E | BIC |
| 8380 | MTAW | MONROE TRACTOR AND IMPLEMENT CO INC | | | SCAC4 |
| 8381 | MTAX | MTAX Corp. | added 7/1988; 1/1994; eliminated 4/1996; 7/2000-7/2005 (not listed) | | NAKINA |
| 8382 | MTAX | MTAX Corp. | added 7/88; 1/94; eliminated 4/96; 7/2000 | | NRHS |
| 8383 | MTAX | *MASS TRANSIT ADMINISTRATION | | | PWRC |
| 8384 | MTAX | +MTAX CORPORATION | | | PWRC |
| 8385 | MTAX | MTAX Corporation | | | RSRV |
| 8386 | MTAY | M TRANSPORT | | | SCAC4 |
| 8387 | MTB | Aerotaxis Metropolitanos, S.A. de C.V. | Callsign: Aerometropolis, | MEX | AVCODES |
| 8388 | MTB | Aerotaxis Metropolitanos | | | ICAO1 |
| 8389 | MTB | Förderverein für die Müglitztalbahn e.V | | DE | VKM |
| 8390 | MTBB | M3O TRANSPORT LLC | | | SCAC4 |
| 8391 | MTBC | MONTGOMERY TRANSPORT LLC | | | SCAC4 |
| 8392 | MTBD | MADRID TRUCKING | | | SCAC4 |
| 8393 | MTBG | MORAN TANK BARGE COMPANY | | | SCAC4 |
| 8394 | MTBH | MACDONALD, TOM TRUCKING LTD | | | SCAC4 |
| 8395 | MTBK | MID THUMB TRUCKING CO | | | SCAC4 |
| 8396 | MTBM | MARTINEZ GARCIA, JOSE | | | SCAC4 |
| 8397 | MTBP | MONTGOMERY TRANSPORTATION BROKERS I | | | SCAC4 |
| 8398 | MTBQ | MAXLAND TRUCKING INC | | | SCAC4 |
| 8399 | MTBT | MATTER, BERT INC | | | SCAC4 |
| 8400 | MTBU | MULTIBOXX LIMITED | | HK | BIC |
