| 7401 | MRKE | MARK LINE DISTRIBUTORS INC | | | SCAC4 |
| 7402 | MRKF | MERKL FARMS | | | SCAC4 |
| 7403 | MRKG | MASTER TRUCKING LTD | | | SCAC4 |
| 7404 | MRKI | MERIT TRUCKING CO | | | SCAC4 |
| 7405 | MRKJ | MARK IV TRANSPORTATION & LOGISTICS | | | SCAC4 |
| 7406 | MRKK | MARS TRUCKING INC | | | SCAC4 |
| 7407 | MRKL | MARKELL TRANSPORT LTD | | | SCAC4 |
| 7408 | MRKM | MARKSM | | | SCAC4 |
| 7409 | MRKN | MR TRUCKING INC | | | SCAC4 |
| 7410 | MRKP | MARCO TRANSPORT INC | | | SCAC4 |
| 7411 | MRKQ | MATTRACKS INC | | | SCAC4 |
| 7412 | MRKS | MERIKANS | | | SCAC4 |
| 7413 | MRKT | MARKTECH | | | SCAC4 |
| 7414 | MRKU | MAERSK A/S | | DK | BIC |
| 7415 | MRKU | A P MOLLER | | | SCAC4 |
| 7416 | MRKV | MORA TRUCKING INC | | | SCAC4 |
| 7417 | MRKW | MARINA TANKER CORPORATION | | | SCAC4 |
| 7418 | MRL | Aeromorelos S.A. de C.V. | Callsign: Aeromorelos, | MEX | AVCODES |
| 7419 | MRL | Aeromorelos | | | ICAO1 |
| 7420 | MRL | Montana RailLink, Inc. | added 4/1988; 1/1994-7/2005 | | NAKINA |
| 7421 | MRL | Montana RailLink, Inc. | added 4/88; 1/94-7/2000 | | NRHS |
| 7422 | MRL | MONTANA RAIL LINK, INC. [CODE FORMERLY ASSIGNED TO MEADOW RIVER LUMBER] | | | PWRC |
| 7423 | MRL | Montana Rail Link | | | RSRV |
| 7424 | MRL | MONTANA RAIL LINK INC | | | SCAC4 |
| 7425 | MRL | Montana Raillink Inc. | | USA | TRAFFIC |
| 7426 | MRL | Mendip Rail Limited | | UK | VKM |
| 7427 | MRLC | MARTIN TRANSPORTATION SYSTEMS INC | | | SCAC4 |
| 7428 | MRLD | MIRACLE, R L DIST CO INC | | | SCAC4 |
| 7429 | MRLF | MCCROSKEY RANCHES LLC | | | SCAC4 |
| 7430 | MRLG | MORNINGSTAR LOGISTICS LLC | | | SCAC4 |
| 7431 | MRLH | MASON, ROBERT LOBSTER INC | | | SCAC4 |
| 7432 | MRLI | MOTOR RAIL DELIVERY INC | | | SCAC4 |
| 7433 | MRLJ | MARRLIN TRANSIT INC | | | SCAC4 |
| 7434 | MRLL | M R L A TRANSPORTES S DE RL DE CV | | | SCAC4 |
| 7435 | MRLM | Minneapolis, Red Lake and Manitoba Ry. Co. | 4/1938 | | NAKINA |
| 7436 | MRLM | Minneapolis, Red Lake and Manitoba Ry. Co. | Apr-38 | | NRHS |
| 7437 | MRLM | MINNEAPOLIS, RED LAKE & MANITOBA RWY. CO. | | | PWRC |
| 7438 | MRLO | MERLO TRUCKING | | | SCAC4 |
| 7439 | MRLQ | METRO LEASING LLC | | | SCAC4 |
| 7440 | MRLR | MORALES TRUCKING | | | SCAC4 |
| 7441 | MRLS | MATRIX LOGISTICS | | | SCAC4 |
| 7442 | MRLT | MARLIN TRANSPORT LLC | | | SCAC4 |
| 7443 | MRLT | Mineral Resources Limited | | AUS | TRAFFIC |
| 7444 | MRLU | A P MOLLER | | | SCAC4 |
| 7445 | MRLV | MIDTOWN RV LTD | | | SCAC4 |
| 7446 | MRLX | Mid America Railcar Leasing LLC | added 10/2003; eliminated 4/2004; 7/2005 (not listed) | | NAKINA |
| 7447 | MRLX | Morris & Co. Refrigerator Lines (Armour Car Lines) | 7/1923-7/1932 | | NAKINA |
| 7448 | MRLX | Morris & Co. Refrigerator Line | 8/1920 | | NAKINA |
| 7449 | MRLX | *ARMOUR CAR LINES [MORRIS & CO. REFRIGERATOR LINE] | | | PWRC |
| 7450 | MRLX | +MID AMERICA RAILCAR LEASING | | | PWRC |
| 7451 | MRLX | Mid America Railcar Leasing | | | RSRV |
| 7452 | MRLX | MID AMERICA RAILCAR LEASING LLC | | | SCAC4 |
| 7453 | MRLX | Mid-America Railcar Leasing | | USA | TRAFFIC |
| 7454 | MRLY | MORLEY, T M INC | | | SCAC4 |
| 7455 | MRLZ | MEADOW RIVER LUMBER | | | PWRC |
| 7456 | MRM | Aerocharter, Inc. | Callsign: Maritime, | CDN | AVCODES |
| 7457 | MRM | Murmansk Aviation Enterprise, LLC | Callsign: Murman, | RUS | AVCODES |
| 7458 | MRM | Aerocharter | | | ICAO1 |
| 7459 | MRM | MIDLAND RAILWAY OF MANITOBA | | | PWRC |
| 7460 | MRMB | MEDINA REYNA, MARIA GABRIELA | | | SCAC4 |
| 7461 | MRMC | MRM SPECIALIZED TRUCKING | | | SCAC4 |
| 7462 | MRMD | MARIMED SHIPPING INC | | | SCAC4 |
| 7463 | MRMF | MENTOR MEDIA LTD | | | SCAC4 |
| 7464 | MRMG | MONROE TOOL AND MANUFACTURING | | | SCAC4 |
| 7465 | MRMH | MOTORES MENDEZ | | | SCAC4 |
| 7466 | MRMI | MARTINEZ REYNA, MIGUEL | | | SCAC4 |
| 7467 | MRMJ | MARTINEZ MARDUENO, JUAN | | | SCAC4 |
| 7468 | MRMN | MARME | | | SCAC4 |
| 7469 | MRMO | MORALES, MANUEL AND MORALES, ARTURO | | | SCAC4 |
| 7470 | MRMQ | MITRANO REMOVAL SERVICE LLC | | | SCAC4 |
| 7471 | MRMR | MORGAN RAMIREZ, MIGUEL GUILLERMO | | | SCAC4 |
| 7472 | MRMS | MURPHY MOVING & STORAGE INC | | | SCAC4 |
| 7473 | MRMT | MRM TRUCKING | | | SCAC4 |
| 7474 | MRMU | GCATAINER BV | | | SCAC4 |
| 7475 | MRMV | MIDDLE RIVER MARINE SERVICE | | | SCAC4 |
| 7476 | MRMX | Midwest Railcar Corp. | added 4/2007 | | NAKINA |
| 7477 | MRMX | MRMX Leasing & Management, LLC | 7/2005 (not listed) | | NAKINA |
| 7478 | MRMX | MIDWEST RAILCAR CORP. [MRMX LEASING & MANAGEMENT, LLC] | | | PWRC |
| 7479 | MRMX | MRMX Leasing and Management | | | RSRV |
| 7480 | MRMX | MIDWEST RAILCAR CORPORATION | | | SCAC4 |
| 7481 | MRMY | MR M LLC | | | SCAC4 |
| 7482 | MRMZ | MONTICELLO RAILWAY MUSEUM | | | PWRC |
| 7483 | MRMZ | Monticello Railway Museum | | | RSRV |
| 7484 | MRN | Missions Gouvernementales Francaises | Callsign: Marianne, | F | AVCODES |
| 7485 | MRN | Air Marne | | F | AVCODES |
| 7486 | MRN | Missions Gouvernemtales Francaises | | | ICAO1 |
| 7487 | MRNA | MOORE, IAN, DR | | | SCAC4 |
| 7488 | MRNB | MONTGOMERY, RON TRUCKING INC | | | SCAC4 |
| 7489 | MRNF | MARINOS FUEL OILS INC | | | SCAC4 |
| 7490 | MRNG | MARTIN TRUCKING | | | SCAC4 |
| 7491 | MRNK | MORENOS TRANSFERS | | | SCAC4 |
| 7492 | MRNL | MOTOR RACING NETWORK INC | | | SCAC4 |
| 7493 | MRNO | MORTON MOTOR EXPRESS INC | | | SCAC4 |
| 7494 | MRNP | MIRACLE TRANSPORTATION INC | | | SCAC4 |
| 7495 | MRNQ | MERCURY TRANS | | | SCAC4 |
| 7496 | MRNR | MCCOLL RACING ENTERPRISES INC | | | SCAC4 |
| 7497 | MRNT | MORAN TOWING CORP | | | SCAC4 |
| 7498 | MRNU | MARINETEC LTD | | RUS | BIC |
| 7499 | MRNV | MARTINS SPECIALIZED TRANSPORT INC | | | SCAC4 |
| 7500 | MRNX | (NATX) RETIRED 06-24-92 ATP | | | PWRC |
