| 6801 | MPKC | METRO PACKAGING CORP | | | SCAC4 |
| 6802 | MPKD | MACPACK LLC | | | SCAC4 |
| 6803 | MPKG | MARPAU TRUCKING | | | SCAC4 |
| 6804 | MPKI | METPLAS TRUCKING | | | SCAC4 |
| 6805 | MPKN | M P K TRUCKING | | | SCAC4 |
| 6806 | MPKO | MPK Olsztyn | | PL | TRAFFIC |
| 6807 | MPKOS | Miejskie Przedsiębiorstwo Komunikacji w Ostrowcu Świętokrzyskim | | PL | TRAFFIC |
| 6808 | MPKR | MACPHAI | | | SCAC4 |
| 6809 | MPKSLU | MPK Slupsk | | PL | TRAFFIC |
| 6810 | MPKT | MEHRAN PACIFIC TRUCKING LTD | | | SCAC4 |
| 6811 | MPKU | POLYGON MPK, LLC | | BY | BIC |
| 6812 | MPKX | Sunburst Cattle Co. | added 7/1973; 1/1975; eliminated 4/1976 | | NAKINA |
| 6813 | MPKX | Marhoefer Packing Co., Inc. | 4/1970; eliminated 7/1973 | | NAKINA |
| 6814 | MPKX | Michigan Pickle Co. | 1/1950-1/1952; eliminated 7/1954 | | NAKINA |
| 6815 | MPKX | Michigan Pickle Co. | Jan-52 | | NRHS |
| 6816 | MPKX | Marhoefer Packing Co., Inc. | 4/70; eliminated 7/73 | | NRHS |
| 6817 | MPKX | Sunburst Cattle Co. | added 7/73; 1/75; eliminated 4/76 | | NRHS |
| 6818 | MPKX | *MICHIGAN PICKLE CO. | | | PWRC |
| 6819 | MPKX | *MARHOEFER PACKING CO. | | | PWRC |
| 6820 | MPKX | *SUNBURST CATTLE CO. | | | PWRC |
| 6821 | MPKX | SUNBURST CATTLE CO. | | | SCAC4 |
| 6822 | MPL | Master Planner, Inc. | | USA | AVCODES |
| 6823 | MPL | Metropolitan Airways Ltd. | Callsign: Metro, | GB | AVCODES |
| 6824 | MPL | Master Planner | | | ICAO1 |
| 6825 | MPL | MISSISSIPPI POWER & LIGHT | | | PWRC |
| 6826 | MPL | MORIS Sp. z o.o. | | PL | VKM |
| 6827 | MPLB | M & P LOGISTICS I, LP | | | SCAC4 |
| 6828 | MPLD | MONTREAL PIPE LINE LIMITED | | | SCAC4 |
| 6829 | MPLF | M & P LOGISTICS LLC | | | SCAC4 |
| 6830 | MPLG | MAPLES GAS CO INC | | | SCAC4 |
| 6831 | MPLH | MERTENS, PAUL H | | | SCAC4 |
| 6832 | MPLI | Minnesota Prairie Line Inc. | added 10/2002; 7/2005 | | NAKINA |
| 6833 | MPLI | MINNESOTA PRAIRIE LINE, INC. | | | PWRC |
| 6834 | MPLI | Minnesota Prairie Line | | | RSRV |
| 6835 | MPLI | MINNESOTA PRAIRIE LINE INC | | | SCAC4 |
| 6836 | MPLK | MOSAIC PLANET | | | SCAC4 |
| 6837 | MPLM | MP LINE DE MEXICO SA DE CV | | | SCAC4 |
| 6838 | MPLN | M P L MFG INC | | | SCAC4 |
| 6839 | MPLO | MARTIN PALLET INC | | | SCAC4 |
| 6840 | MPLQ | MAPLE TRANSPORTATION LLC | | | SCAC4 |
| 6841 | MPLR | MASTERPIECE INTERNATIONAL LIMITED | | | SCAC4 |
| 6842 | MPLT | MILLER, PAUL TRUCKING INC | | | SCAC4 |
| 6843 | MPLW | MOVING PERFORMANCE LLC | | | SCAC4 |
| 6844 | MPLX | General Electric Railcar Services Corp. | added 1/1984; 1/1994; eliminated 10/1994 | | NAKINA |
| 6845 | MPLX | North American Car Corp. | added 4/1973; 1/1975-1/1980; eliminated 1/1984 | | NAKINA |
| 6846 | MPLX | Marhoefer Packing Co., Inc. | added 1/1969 | | NAKINA |
| 6847 | MPLX | American Oil Co. | added 10/1954; 10/1957; eliminated 4/1961 | | NAKINA |
| 6848 | MPLX | Mexican Petroleum Corp. | 7/1923-7/1954; eliminated 10/1954 | | NAKINA |
| 6849 | MPLX | Mexican Petroleum Co. (Mexican Petroleum Corp.) | 8/1920 | | NAKINA |
| 6850 | MPLX | Mexican Petroleum Corp. | 4/38-1/52 | | NRHS |
| 6851 | MPLX | American Oil Co. | 10/57; eliminated 4/61 | | NRHS |
| 6852 | MPLX | Marhoefer Packing Co., Inc. | added 1/69 | | NRHS |
| 6853 | MPLX | North American Car Corp. | added 4/73; 1/75-1/80 | | NRHS |
| 6854 | MPLX | General Electric Railcar Services Corp. | 1/94; eliminated 10/94 | | NRHS |
| 6855 | MPLX | *AMERICAN OIL CO [MEXICAN PETROLEUM CORP.] | | | PWRC |
| 6856 | MPLX | *MARHOEFER PACKING CO., INC. | | | PWRC |
| 6857 | MPLX | *(NATX) G. E. RAILCAR SERVICES CORP. [MOUNTAIN PINE LUMBER LTD.] | | | PWRC |
| 6858 | MPLX | GE Rail Services | | | RSRV |
| 6859 | MPLZ | *MINNESOTA POWER & LIGHT CO. | | | PWRC |
| 6860 | MPLZ | *UNION PACIFIC RAILROAD COMPANY | | | PWRC |
| 6861 | MPLZ | Missouri Pacific Railroad (Union Pacific Railroad) | | | RSRV |
| 6862 | MPMC | MOUNTAIN PETROLEUM LLC | | | SCAC4 |
| 6863 | MPME | MPM ENGINEERING LTD | | | SCAC4 |
| 6864 | MPMG | MARQUEZ PAREDES, MIGUEL | | | SCAC4 |
| 6865 | MPMH | MACHINE & PRODUCT MOVERS OF OHIO IN | | | SCAC4 |
| 6866 | MPML | MAINROAD PAVEMENT MARKING LIMITED P | | | SCAC4 |
| 6867 | MPMP | MOTOR SPORTS MEDICINE GROUP INC | | | SCAC4 |
| 6868 | MPMR | MONTEREY PENINSULA MOVERS | | | SCAC4 |
| 6869 | MPMU | MOMENTIVE PERFORMANCE MATERIALS GMBH | | D | BIC |
| 6870 | MPMU | MOMENTIV | | | SCAC4 |
| 6871 | MPMV | MODERN PIANO MOVING | | | SCAC4 |
| 6872 | MPMX | Marathon Corp. | 1/1945-10/1957; eliminated 4/1958 | | NAKINA |
| 6873 | MPMX | Marathon, a Division of American Can Co. | added 4/1958; eliminated 7/1959 | | NAKINA |
| 6874 | MPMX | Marathon Paper Mills Co. | 7/1937-1/1943 | | NAKINA |
| 6875 | MPMX | Marathon Paper Mills Co. | Apr-38 | | NRHS |
| 6876 | MPMX | Marathon Corp. | 1/52-10/57 | | NRHS |
| 6877 | MPMX | Marathon, a Division of American Can Co. | eliminated 7/59 | | NRHS |
| 6878 | MPMX | MARATHON, DIV. AMERICAN CAN CO. [MARATHON PAPER MILLS} | | | PWRC |
| 6879 | MPNF | METRO PARCEL & FREIGHT INC | | | SCAC4 |
| 6880 | MPNI | MILTON PROPANE INC | | | SCAC4 |
| 6881 | MPNL | MEGACORP LINES LLC | | | SCAC4 |
| 6882 | MPNT | MICHIGAN PIONEER TRANSPORT INC | | | SCAC4 |
| 6883 | MPO | Transportes Aereos Amparo, S.A. de C.V. | Callsign: Amparo, | MEX | AVCODES |
| 6884 | MPO | Transportes Aereos Amparo | | | ICAO1 |
| 6885 | MPO | Metropolitano | Real: MP | RA | TRAFFIC |
| 6886 | MPOI | MARCO POLO LOGISTICS (LAX) INC | | | SCAC4 |
| 6887 | MPOM | METROPOLITAN MOVERS INC | | | SCAC4 |
| 6888 | MPON | MARCOPPOLO TRANSPORT | | | SCAC4 |
| 6889 | MPOP | MUTUAL PROPANE | | | SCAC4 |
| 6890 | MPOR | MELARD TRUCKING | | | SCAC4 |
| 6891 | MPOX | Merchants' & Planters' Oil Co. | 8/1920-7/1935; 7/1937 (not listed) | | NAKINA |
| 6892 | MPOX | MERCHANTS' & PLANTERS' OIL CO. | | | PWRC |
| 6893 | MPP | MANITOU & PIKE'S PEAK RAILROAD CO. | | | PWRC |
| 6894 | MPPD | MARSHALL, PAUL PRODUCE INC | | | SCAC4 |
| 6895 | MPPE | MID PAC PETROLEUM LLCGOLD BOND BUIL | | | SCAC4 |
| 6896 | MPPN | MEDPARTS PLUS INC | | | SCAC4 |
| 6897 | MPPT | MOORE PETROLEUM PRODUCTS | | | SCAC4 |
| 6898 | MPPW | MPP CONTAINER AS | | | SCAC4 |
| 6899 | MPPX | Montana Phosphate Products Co. | added 7/1955; eliminated 4/1956 | | NAKINA |
| 6900 | MPPX | Montana Phosphate Products Co. | added 7/55 | | NRHS |
