| 3501 | MH | Mount Hood R.R. | added 1/89; eliminated 10/89 | | NRHS |
| 3502 | MH | Mount Hood R.R. Co. | Jul-00 | | NRHS |
| 3503 | MH | MT. HOOD RAILROAD COMPANY | | | PWRC |
| 3504 | MH | Mount Hood Railroad | | | RSRV |
| 3505 | MH | MT HOOD RAILROAD CO | | | SCAC4 |
| 3506 | MH | Mohawk & Hudson | | USA | TRAFFIC |
| 3507 | MH | Museumseisenbahn Hanau e.V. | | DE | VKM |
| 3508 | MH&W | Hill City Ry. Co. | 8/1920 | | NAKINA |
| 3509 | MH&W | HILL CITY RWY. CO. | | | PWRC |
| 3510 | MHA | Mountain High Aviation | Callsign: Mountain High, | USA | AVCODES |
| 3511 | MHA | Anglian Air Taxis | Callsign: Anglian, | GB | AVCODES |
| 3512 | MHA | Mountain High Aviation | | | ICAO1 |
| 3513 | MHAA | M-TECH | | | SCAC4 |
| 3514 | MHAC | METAL FAB PRO RACE SHOP | | | SCAC4 |
| 3515 | MHAE | MICHAEL, GEORGE | | | SCAC4 |
| 3516 | MHAH | MACRAY HARBOR | | | SCAC4 |
| 3517 | MHAI | MEEHAN TRANSPORT LLC | | | SCAC4 |
| 3518 | MHAK | MOHAWK TRANSPORTATION INC | | | SCAC4 |
| 3519 | MHAN | MEEHA | | | SCAC4 |
| 3520 | MHAR | MARSHA | | | SCAC4 |
| 3521 | MHAT | MEDICINE HAT EXPRESS INC | | | SCAC4 |
| 3522 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | 7/2000-7/2005 (not listed) | | NAKINA |
| 3523 | MHAX | U.S. Dept. of the Interior, Bureau of Land Management, Helium Operations | eliminated 10/1998 | | NAKINA |
| 3524 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/1982; 1/1994 | | NAKINA |
| 3525 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Division of Helium Operations, Amarillo, Texas | added 10/1981; eliminated 7/1982 | | NAKINA |
| 3526 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/1980; eliminated 10/1981 | | NAKINA |
| 3527 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations, Amarillo, Texas | eliminated 7/1980 | | NAKINA |
| 3528 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations | added 7/1971; 1/1975-1/1980 | | NAKINA |
| 3529 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | 10/1966; eliminated 7/1971 | | NAKINA |
| 3530 | MHAX | U.S. Dept. of the Interior, Bureau of Mines | 10/1957-7/1965 | | NAKINA |
| 3531 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | added 7/1955 | | NAKINA |
| 3532 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | added 7/55 | | NRHS |
| 3533 | MHAX | U.S. Dept. of the Interior, Bureau of Mines | 10/57-7/65 | | NRHS |
| 3534 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | Oct-66 | | NRHS |
| 3535 | MHAX | U.S. Dept. of the Interior, Bureau of Mines | Apr-70 | | NRHS |
| 3536 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations | 1/75-1/80 | | NRHS |
| 3537 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations, Amarillo, Texas | eliminated 7/80 | | NRHS |
| 3538 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/80; eliminated 10/81 | | NRHS |
| 3539 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Division of Helium Operations, Amarillo, Texas | added 10/81; eliminated 7/82 | | NRHS |
| 3540 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/82; 1/94 | | NRHS |
| 3541 | MHAX | U.S. Dept. of the Interior, Bureau of Land Management, Helium Opers | eliminated 10/98 | | NRHS |
| 3542 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | Jul-00 | | NRHS |
| 3543 | MHAX | US DEPT. OF THE INTERIOR - BUREAU OF MINES, HELIUM FIELD OPERATIONS, AMARILLO, TX | | | PWRC |
| 3544 | MHAX | United States Department of the Interior Bureau of Mines Helium Field Operations | | | RSRV |
| 3545 | MHAX | USDI-BUR OF MINES,DIV OF HELIUM OPE | | | SCAC4 |
| 3546 | MHAY | MEHERRIN AGRICULTURAL & CHEMICAL CO | | | SCAC4 |
| 3547 | MHBR | MCHUGH BROTHERS | | | PWRC |
| 3548 | MHBU | BATIMPEX | | | SCAC4 |
| 3549 | MHBW | MAESTRO SHIPPING BV | | | SCAC4 |
| 3550 | MHC | Aero Jomacha, S.A. de C.V. | Callsign: Aero Jomacha, | MEX | AVCODES |
| 3551 | MHC | Aero Jomacha | | | ICAO1 |
| 3552 | MHC | MOHALL CENTRAL RAILROAD, INC. | | | PWRC |
| 3553 | MHC | MOHALL CENTRAL RAILROAD INC | | | SCAC4 |
| 3554 | MHCA | MICHAEL, CHRISTOPHER & ASSOCIATES I | | | SCAC4 |
| 3555 | MHCC | MALHA TRANSPORT INC | | | SCAC4 |
| 3556 | MHCD | MATTHES, C. D., INC. | | | SCAC1 |
| 3557 | MHCE | MACHINE CARRIERS | | | SCAC4 |
| 3558 | MHCG | MACKENZIE HEATING AND COOLING INC | | | SCAC4 |
| 3559 | MHCH | MID-SOUTH CONSOLIDATED CHASSIS POOL | | | SCAC4 |
| 3560 | MHCI | MOUNTAIN HIGH CONTRACTORS INC | | | SCAC4 |
| 3561 | MHCK | MOHAWK CUSTOMS AND SHIPPING CO INC | | | SCAC4 |
| 3562 | MHCM | M H C MESSENGERS INC | | | SCAC4 |
| 3563 | MHCN | MILLER HONEY CO INC | | | SCAC4 |
| 3564 | MHCO | Marquette & Huron Mountain R.R. Co., Inc. | 1/1975-1/1980 | | NAKINA |
| 3565 | MHCO | Marquette & Huron Mountain R.R. Co., Inc. | 1/75-1/80 | | NRHS |
| 3566 | MHCO | MARQUETTE & HURON MOUNTAIN RAILROAD CO. | | | PWRC |
| 3567 | MHCO | Marquette and Huron Mountain Railroad | | | RSRV |
| 3568 | MHCP | MCH TRANSPORTATION CO | | | SCAC4 |
| 3569 | MHCQ | MARSHALL CONSTRUCTION CO INC | | | SCAC4 |
| 3570 | MHCR | M H CRUCES INTERNACIONALES | | | SCAC4 |
| 3571 | MHCT | MITSUBISHI CORPORATION | | | SCAC4 |
| 3572 | MHCU | MAG CONTAINER LINES INC | | SY | BIC |
| 3573 | MHCU | MINTURNO CORPORATION | | | SCAC4 |
| 3574 | MHD | Yas Air Kish | Callsign: Yas Air, | IR | AVCODES |
| 3575 | MHDBB | | City: Banska Bystrica | SK | TRAFFIC |
| 3576 | MHDE | MUSH DELIVERY | | | SCAC4 |
| 3577 | MHDM | MONTS ON-TIME EXPRESS INC | | | SCAC4 |
| 3578 | MHDN | MAHDI & SON TRANSPORT INC | | | SCAC4 |
| 3579 | MHDS | MARCHAND, DENIS TRANSPORT | | | SCAC4 |
| 3580 | MHDT | MUIRHEAD TRUCKING INC | | | SCAC4 |
| 3581 | MHDU | MISUBISHI HEAVY INDUSTRIES LTD. | | | SCAC4 |
| 3582 | MHDV | MYHRE, DAVID INC | | | SCAC4 |
| 3583 | MHE | Meppen-Haselünner Eisenbahn | | D | TRAFFIC |
| 3584 | MHEH | MOUNTAIN HIGH EXPRESS | | | SCAC4 |
| 3585 | MHEI | MEREDITH ENTERPRISES INC | | | SCAC4 |
| 3586 | MHEL | M & H EXPRESS LINE LLC | | | SCAC4 |
| 3587 | MHEP | MARIAH EXPRESS INC | | | SCAC4 |
| 3588 | MHEQ | M & H EXPRESS INC | | | SCAC4 |
| 3589 | MHES | MALHI EXPRESS | | | SCAC4 |
| 3590 | MHEV | MASTER HAUL ENTERPRISES INC | | | SCAC4 |
| 3591 | MHF | Maritime Helicopters | Callsign: Air Maritime, | USA | AVCODES |
| 3592 | MHFD | MOHAWK FLUSH DOORS INC | | | SCAC4 |
| 3593 | MHFF | MILE HI FROZEN FOODS CO | | | SCAC1 |
| 3594 | MHFF | MILE HI FROZEN FOODS CO | | | SCAC4 |
| 3595 | MHFG | MOHOFF FREIGHT LINES | | | SCAC4 |
| 3596 | MHFI | MHF INC | | | SCAC4 |
| 3597 | MHFL | MHF LOGISTICAL SOLUTIONS | | | SCAC4 |
| 3598 | MHFM | MILKY HAVEN FARMS | | | SCAC4 |
| 3599 | MHFP | MAPLE HEIGHTS FARMS LLC | | | SCAC4 |
| 3600 | MHFR | MARSH HAVEN FARM | | | SCAC4 |
