| 6601 | MOWX | FORTALEZA CONSTRUCTION COMPANY | | | SCAC4 |
| 6602 | MOWY | MOLERWAY FREIGHT LINES, INC | | | SCAC1 |
| 6603 | MOWY | MOLERWAY FREIGHT LINES INC | | | SCAC4 |
| 6604 | MOWZ | MOTOR WHEEL | | | PWRC |
| 6605 | MOX | MAINTENANCE OF WAY (WORK EQUIPMENT) | | | PWRC |
| 6606 | MOXC | M O | | | SCAC4 |
| 6607 | MOXF | MOSS TRANSPORTATION | | | SCAC4 |
| 6608 | MOXL | MOTEX LOGISTICS LLC | | | SCAC4 |
| 6609 | MOXN | METRO TRANSPORT | | | SCAC4 |
| 6610 | MOXO | MOXIE TRANSPORT INC | | | SCAC4 |
| 6611 | MOXP | MARRERO TRANSPORT LLC | | | SCAC4 |
| 6612 | MOXR | MORRISON EXPRESS CORPORATION (U S A | | | SCAC4 |
| 6613 | MOXV | Moxahala Valley Ry. Co. | added 10/1983; eliminated 10/1987 | | NAKINA |
| 6614 | MOXV | Moxahala Valley Ry. Co. | added 10/83; eliminated 10/87 | | NRHS |
| 6615 | MOXV | MOXAHALA VALLEY RAILWAY CO. | | | PWRC |
| 6616 | MOXV | Moxahala Valley Railway | | | RSRV |
| 6617 | MOYI | MOLO OIL COMPANY | | | SCAC4 |
| 6618 | MOYR | MOYER & SON INC | | | SCAC4 |
| 6619 | MOYT | METRO CITY TRANSPORT | | | SCAC4 |
| 6620 | MOZ | Amadeus Air Luftfahrtgesellschaft mbH | Callsign: Mozart, Ceased operations. | A | AVCODES |
| 6621 | MOZ | SalzburgJetAviation GmbH | Callsign: Mozart, | A | AVCODES |
| 6622 | MP | Martinair Holland N.V. | ICAO: MPH, Callsign: Martinair, IATA Prefix: 129, Name changed from Martin's Luchtvervoermaatschappij (Martin's Aircharter Company M.A.C.) N.V | NL | AVCODES |
| 6623 | MP | Martin's Luchtvervoermaatschappij (Martin's Aircharter Company M.A.C.) N.V | Name changed to Martinair Holland N.V. | NL | AVCODES |
| 6624 | MP | Union Pacific R.R. Co. | added 4/1997; 7/2000-7/2005 | | NAKINA |
| 6625 | MP | Missouri Pacific System | 1/1994; eliminated 4/1997 | | NAKINA |
| 6626 | MP | Missouri Pacific R.R. Co. | 7/1923-10/1966 & 1/1975-1/1980 | | NAKINA |
| 6627 | MP | Missouri Pacific R.R. Co. | 4/38-10/66 & 1/75-1/80 | | NRHS |
| 6628 | MP | Missouri Pacific System | 1/94; eliminated 4/97 | | NRHS |
| 6629 | MP | Union Pacific R.R. Co. | added 4/97; 7/2000 | | NRHS |
| 6630 | MP | UNION PACIFIC [MISSOURI PACIFIC RAILROAD] | | | PWRC |
| 6631 | MP | Missouri Pacific Railroad (Union Pacific Railroad) | | | RSRV |
| 6632 | MP | MISSOURI PACIFIC RAILROAD COMPANY | | | SCAC4 |
| 6633 | MP | Missouri Pacific | | USA | TRAFFIC |
| 6634 | MP&N | Mineral Point & Northern Ry. Co. | 7/1923 | | NAKINA |
| 6635 | MP&N | MINERAL POINT & NORTHERN RWY. CO. | | | PWRC |
| 6636 | MPA | Mid-Pacific Airlines, Inc. | Callsign: Mid Pac, | USA | AVCODES |
| 6637 | MPA | Mid-Pacific Airlines | | | ICAO1 |
| 6638 | MPA | York Ry. Co. | added 4/2000; 7/2000-7/2005 | | NAKINA |
| 6639 | MPA | Maryland & Pennsylvania R.R. Co. | 1/1975-1/1994; eliminated 4/2000 | | NAKINA |
| 6640 | MPA | Maryland & Pennsylvania R.R. Co. | 1/75-1/94; eliminated 4/2000 | | NRHS |
| 6641 | MPA | York Ry. Co. | added 4/2000; 7/2000 | | NRHS |
| 6642 | MPA | YORK RAILWAY CO. [MARYLAND & PENNSYLVANIA RAILROAD] | | | PWRC |
| 6643 | MPA | Maryland and Pennsylvania Railroad (York Railway) | | | RSRV |
| 6644 | MPA | Maryland & Pennsylvania R.R. Co. | | USA | TRAFFIC |
| 6645 | MPAC | MUCCIPAC | | | SCAC4 |
| 6646 | MPAD | MARYLAND PORT AUTHORITY | | | PWRC |
| 6647 | MPAD | MPA | | | SCAC4 |
| 6648 | MPAE | MT PAN ADVENTURE | | | SCAC4 |
| 6649 | MPAF | MAINES PAPER AND FOOD SERVICE INC | | | SCAC4 |
| 6650 | MPAJ | MODA PARA AUTOS S DE RL DE | | | SCAC4 |
| 6651 | MPAK | MASCO PETROLEUM INC | | | SCAC4 |
| 6652 | MPAN | MISSION PRODUCE INC | | | SCAC4 |
| 6653 | MPAP | M P AGRI-PRODUCTS | | | SCAC4 |
| 6654 | MPAQ | MIKES PAINT AND BODY INC | | | SCAC4 |
| 6655 | MPAT | MORENO, PATRICIA | | | SCAC4 |
| 6656 | MPAU | MITSUBISHI POLYCRYSTALLINE SILICON AM CO | | USA | BIC |
| 6657 | MPAV | MANNON EXCAVATING & PAVING CO INC | | | SCAC4 |
| 6658 | MPAW | MT PAN AEGIS | | | SCAC4 |
| 6659 | MPAX | MITSUBISHI POWER SYSTEMS AMERICAS, INC. | | | PWRC |
| 6660 | MPAX | MITSUBISHI POWER SYSTEMS AMERICAS I | | | SCAC4 |
| 6661 | MPBA | MANNING, PATRICK | | | SCAC4 |
| 6662 | MPBD | MP COMBUSTION PROCESS LTD | | | SCAC4 |
| 6663 | MPBI | MOYLE PETROLEUM COMPANY | | | SCAC4 |
| 6664 | MPBK | MINIMUM PRICE BOOKS | | | SCAC4 |
| 6665 | MPBQ | MARTEN TRANSPORT LTD (DEDICATED DIV | | | SCAC4 |
| 6666 | MPBT | MERLIN SHIPPING LLC | | | SCAC4 |
| 6667 | MPBU | LLC REFPEREVOZKY | | RUS | BIC |
| 6668 | MPC | Mountain Pacific Air Ltd. | Callsign: Mountain Pacific, | CDN | AVCODES |
| 6669 | MPC | Mountain Pacific Air | | | ICAO1 |
| 6670 | MPCB | MANDA PACKING COMPANY | | | SCAC4 |
| 6671 | MPCC | MASTER PETROLEUM CO INC | | | SCAC4 |
| 6672 | MPCD | MPC | | | SCAC4 |
| 6673 | MPCE | MAPLE DONUTS INC | | | SCAC4 |
| 6674 | MPCH | MARDESPACHOS | | | SCAC4 |
| 6675 | MPCJ | MOSS, PIERRE C | | | SCAC4 |
| 6676 | MPCL | MILES CHEMICAL COMPANY INC | | | SCAC4 |
| 6677 | MPCO | MPC TRUCKING LLC | | | SCAC4 |
| 6678 | MPCP | MONOPAN CA INC | | | SCAC4 |
| 6679 | MPCS | MATERA PAPER COMPANY INC | | | SCAC4 |
| 6680 | MPCT | MAXIM PRODUCTION COMPANY, LP | | | SCAC4 |
| 6681 | MPCV | MONTECALVO PAVING CORP | | | SCAC4 |
| 6682 | MPCW | MISSISSIPP | | | SCAC4 |
| 6683 | MPCX | Michels Corp. | 7/2005; eliminated 7/2008 | | NAKINA |
| 6684 | MPCX | Michaels Corp. | added 4/2003 | | NAKINA |
| 6685 | MPCX | Michaels Pipeline Construction, Inc. | added 4/1991; 1/1994-7/2000; eliminated 4/2003 | | NAKINA |
| 6686 | MPCX | Moyer Packing Co. | added 10/1981; eliminated 1/1987 | | NAKINA |
| 6687 | MPCX | Mobil Oil Co., a Division of Socony Mobil Oil Co., Inc. | eliminated 10/1962 | | NAKINA |
| 6688 | MPCX | Socony Mobil Oil Co., Inc. | 4/1961 | | NAKINA |
| 6689 | MPCX | Mobil Oil Co., a Division of Socony Mobil Oil Co., Ltd. | added 1/1960 | | NAKINA |
| 6690 | MPCX | Magnolia Petroleum Co. | 8/1920-10/1957; eliminated 1/1960 | | NAKINA |
| 6691 | MPCX | Magnolia Petroleum Co. | 4/38-10/57; eliminated 1/60 | | NRHS |
| 6692 | MPCX | Mobil Oil Co., a Division of Socony Mobil Oil Co., Ltd. | added 1/60 | | NRHS |
| 6693 | MPCX | Socony Mobil Oil Co., Inc. | Apr-61 | | NRHS |
| 6694 | MPCX | Moyer Packing Co. | added 10/81; eliminated 1/87 | | NRHS |
| 6695 | MPCX | Michels Pipeline Construction, Inc. | added 4/91; 1/94-7/2000 | | NRHS |
| 6696 | MPCX | *SOCONY MOBIL OIL CO. [MAGNOLIA PETROLEUM CO.] | | | PWRC |
| 6697 | MPCX | *MOYER PACKING CO. | | | PWRC |
| 6698 | MPCX | Moyer Packing (Michels Pipeline Construction) | | | RSRV |
| 6699 | MPCX | MICHELS CORPORATION | | | SCAC4 |
| 6700 | MPCY | MAPLE CITY TRUCKING INC | | | SCAC4 |
