| 1 | MU | China Eastern Airlines | ICAO: CES, Callsign: China Eastern, IATA Prefix: 781, Formerly CAAC Shanghai region | PRC | AVCODES |
| 2 | MU | Misr Air | Callsign: Misair, | ET | AVCODES |
| 3 | MU | Middletown & Unionville R.R. | 4/1938 | | NAKINA |
| 4 | MU | Middletown & Unionville R.R. | Apr-38 | | NRHS |
| 5 | MU | MIDDLETOWN & UNIONVILLE RAILROAD | | | PWRC |
| 6 | MUA | Murray Air, Inc. | IATA: 5M, Callsign: Murray Air, IATA Prefix: 416, Name changed to National Air Cargo Group, Inc. d/b/a National Airlines. Name changed from Murray Aviation, Inc. | USA | AVCODES |
| 7 | MUA | Murray Aviation, Inc. | Callsign: Murray Air, Name changed to Murray Air | USA | AVCODES |
| 8 | MUA | National Air Cargo Group, Inc. d/b/a National Airlines | IATA: N8, Callsign: Murray Air, IATA Prefix: 416, Name changed from Murray Air, Inc. ICAO designator changed to NCR. Name changed from Murray Aviation, Inc. | USA | AVCODES |
| 9 | MUA | Murray Air | | | ICAO1 |
| 10 | MUA | MUA - Mediterranea Umbro Aretina | 1956 - 1979 | I | TRAFFIC |
| 11 | MUAA | MUMA, ROGER MUSICAL INSTRUMENTS | | | SCAC4 |
| 12 | MUAC | MUNOZ FLORES, GUADALUPE | | | SCAC4 |
| 13 | MUAD | MUSGROVE LOGISTICS INC | | | SCAC4 |
| 14 | MUAF | MULLEN CRANE & TRANSPORT INC | | | SCAC4 |
| 15 | MUAL | MUSICK LIVESTOCK LLC | | | SCAC4 |
| 16 | MUAN | MAUI PETROLEUM INC | | | SCAC4 |
| 17 | MUAO | MULTI SERVICES INTERMODAL CORP | | | SCAC4 |
| 18 | MUAV | MUSTANG BULK CARRIERS INC | | | SCAC4 |
| 19 | MUAY | MURRAY LEASING LLC | | | SCAC4 |
| 20 | MuBB | Museumsbahn Bremerhaven-Bederkesa e.V. | Bederkesa | D | privat-bahn.de |
| 21 | MUBC | MCKEN HUNTING | | | SCAC4 |
| 22 | MUBE | MUELLER BROTHERS TIMBER INC | | | SCAC4 |
| 23 | MUBO | MOOSE TRUCKING | | | SCAC4 |
| 24 | MUC | Air Munich Aviation AG | Callsign: Air Munich, | D | AVCODES |
| 25 | MUCC | MUCCI, PIETRO INC | | | SCAC4 |
| 26 | MUCI | MOUNT CITY TRUCKING INC | | | SCAC4 |
| 27 | MUCN | M & A TRUCKING | | | SCAC4 |
| 28 | MUCO | MOULTRIE TRANSPORTATION | | | SCAC4 |
| 29 | MUCR | MILLENIUM TRANSPORTATION & LOGISTIC | | | SCAC4 |
| 30 | MUCS | MANUFACTURERS CONSOLIDATION SERVICES, INC. | | | SCAC1 |
| 31 | MUCS | MATHIEU, JOCELYN TRANSIT | | | SCAC4 |
| 32 | MUCU | G.T.S SPA | | I | BIC |
| 33 | MUCU | G T S SRL | | | SCAC4 |
| 34 | MUCX | Murro Chemical Co., Inc. | 7/1965-1/1975; eliminated 7/1976; eliminated 10/1978 | | NAKINA |
| 35 | MUCX | Murro Chemical Co., Inc. | 7/65-1/75; eliminated 7/76; eliminated 10/78 | | NRHS |
| 36 | MUCX | MURRO CHEMICAL CO. | | | PWRC |
| 37 | MUCZ | MURPHY COMPANY | | | PWRC |
| 38 | MUDA | MULDER, ART & SONS TRUCKING INC | | | SCAC4 |
| 39 | MUDG | MUDGETT, GEORGE D | | | SCAC4 |
| 40 | MUDN | MURDEN DELIVERY SERVICE INC | | | SCAC4 |
| 41 | MUDR | MUDDY RIVER TRANSPORTATION LLC | | | SCAC4 |
| 42 | MUEC | Modell- und Eisenbahnclub -Rehau e.V | | DE | VKM |
| 43 | MUEI | MUSTANG EXPEDITING INC | | | SCAC4 |
| 44 | MUEL | MUELLER & SONS LLC | | | SCAC4 |
| 45 | MUET | MUELLER TRANSPORTATION INC | | | SCAC4 |
| 46 | MUEU | INT. SPEDITION H. MULLER GMBH | | | SCAC4 |
| 47 | MUFC | MURPHY FUEL CORP | | | SCAC4 |
| 48 | MUFE | MUFFET TRUCKING EXPRESS LLC | | | SCAC4 |
| 49 | MUFERGA | Museo del Ferrocarril de Galicia | | E | TRAFFIC |
| 50 | MUFM | MUFFLERMAN | | | SCAC4 |
| 51 | MUG | Muk Air (GH) Ltd. | Callsign: Muggan, Ceased operations. | GH | AVCODES |
| 52 | MUGC | MULTI LOGISTICS SOLUTIONS INC | | | SCAC4 |
| 53 | MUGG | MUGU GROWERS INC | | | SCAC4 |
| 54 | MUGL | MUNGLE TRUCKING INC | | | SCAC4 |
| 55 | MUGS | MARCUM TRUCKING AND SONS | | | SCAC4 |
| 56 | MUHL | Betriebe der Stadt Mühlheim | | D | TRAFFIC |
| 57 | MUHT | MUHL TRANSPORT | | | SCAC4 |
| 58 | MUHU | MUSTANG JSC | | | SCAC4 |
| 59 | MUI | Trans Air | IATA: P6, Callsign: Maui, IATA Prefix: 356, Designator P6 recalled by IATA | USA | AVCODES |
| 60 | MUI | Trans Executive Airlines of Hawaii t/a transair Express | IATA: 5H, Callsign: Maui, Operates transair Express SD360 Fleet. Designator 5H recalled by IATA | USA | AVCODES |
| 61 | MUI | Trans Executive Airlines of Hawaii t/a transair Express | IATA: R9, Callsign: Maui, Operates transair Express SD360 Fleet. ICAO callsign changed to Transair. Designator 5H recalled by IATA | USA | AVCODES |
| 62 | MUI | Trans Air | Callsign: Maui, Designator P6 recalled by IATA | USA | AVCODES |
| 63 | MUI | Trans Executive Airlines of Hawaii t/a transair Express | IATA: R9, Callsign: Transair, Operates transair Express SD360 Fleet. ICAO callsign changed from Maui. Designator 5H recalled by IATA | USA | AVCODES |
| 64 | MUI | Trans Air | | | ICAO1 |
| 65 | MUII | M C U INTERMODAL INC | | | SCAC4 |
| 66 | MUIK | MITSUI-SOKO CO LTD | | | SCAC4 |
| 67 | MUIR | MUIRS CARTAGE LIMITED | | | SCAC4 |
| 68 | MUJJ | MULLIS TRUCKING | | | SCAC4 |
| 69 | MUK | Muk Air | IATA: ZR, Callsign: Mukair, IATA Prefix: 796, Designator ZR recalled by IATA | DK | AVCODES |
| 70 | MUK | Muk Air | Callsign: Mukair, Ceased operations on 05 November 2001. Designator ZR recalled by IATA | DK | AVCODES |
| 71 | MUKC | MONK TRUCKING CO LLC | | | SCAC4 |
| 72 | MUKE | MUSKET TRANSPORT LTD, THE | | | SCAC4 |
| 73 | MUKF | MUNDO TRUCKING INC | | | SCAC4 |
| 74 | MUKG | MARS TRUCKING | | | SCAC4 |
| 75 | MUKI | MAR TRUCKING | | | SCAC4 |
| 76 | MUKL | MORT TRUCKING LLC | | | SCAC4 |
| 77 | MUKN | MULLIKIN, MICHAEL L TRUCKING CO | | | SCAC4 |
| 78 | MUKO | MAXWELL, ROBERT TRUCKING LTD | | | SCAC4 |
| 79 | MUKT | MUSKOKA TRANSPORT LIMITED | | | SCAC4 |
| 80 | MUKU | DEN HARTOGH GLOBAL BV | | NL | BIC |
| 81 | MUKU | MUTO CO LTD | | | SCAC4 |
| 82 | MUKY | MOUNTAIN CREEK TAXIDERMY | | | SCAC4 |
| 83 | MUL | Mokulele Flight Service, Inc. | IATA: MW, Callsign: Mokulele, IATA Prefix: 415, ICAO designator changed to MHO. ICAO designator changed from BUG. ICAO callsign changed from Speedbuggy. IATA designator changed from 5Z* | USA | AVCODES |
| 84 | MULA | MCCORMICKS USA LOGISTICS INCORPORAT | | | SCAC4 |
| 85 | MULC | MAGNUM LOGISTICS | | | SCAC4 |
| 86 | MULC | Mulleys Coaches | | GB | TRAFFIC |
| 87 | MULD | MULTI-LOAD TRANSPORT INC | | | SCAC4 |
| 88 | MULE | MULTIMATIC TECHNICAL CENTRE (DIV OF | | | SCAC4 |
| 89 | MULG | MULGREW OIL CO | | | SCAC4 |
| 90 | MULH | MULTI TECH | | | SCAC4 |
| 91 | MULH | Soléa | City: Mulhouse | F | TRAFFIC |
| 92 | MULI | MULTIMODAL INTERNATIONAL SHIPPING I | | | SCAC4 |
| 93 | MULL | MULLINS LEASING SERVICE INC | | | SCAC4 |
| 94 | MULLER | Müller Gleisbau AG | | CH | TRAFFIC |
| 95 | MULM | MULLEN TRUCKING LP | | | SCAC4 |
| 96 | MULN | MULLEN BROS OF NORTH ADAMS MASS INC | | | SCAC4 |
| 97 | MULO | MULLER TRANSPORT | | | SCAC4 |
| 98 | MULQ | MULTILINE TRANSPORT LTD | | | SCAC4 |
| 99 | MULT | MULE TEAM EXPRESS INC | | | SCAC4 |
| 100 | MULV | MULVANIA TRUCKING CO | | | SCAC4 |
