| 1 | MHA | Mountain High Aviation | Callsign: Mountain High, | USA | AVCODES |
| 2 | MHA | Anglian Air Taxis | Callsign: Anglian, | GB | AVCODES |
| 3 | MHA | Mountain High Aviation | | | ICAO1 |
| 4 | MHAA | M-TECH | | | SCAC4 |
| 5 | MHAC | METAL FAB PRO RACE SHOP | | | SCAC4 |
| 6 | MHAE | MICHAEL, GEORGE | | | SCAC4 |
| 7 | MHAH | MACRAY HARBOR | | | SCAC4 |
| 8 | MHAI | MEEHAN TRANSPORT LLC | | | SCAC4 |
| 9 | MHAK | MOHAWK TRANSPORTATION INC | | | SCAC4 |
| 10 | MHAN | MEEHA | | | SCAC4 |
| 11 | MHAR | MARSHA | | | SCAC4 |
| 12 | MHAT | MEDICINE HAT EXPRESS INC | | | SCAC4 |
| 13 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | 7/2000-7/2005 (not listed) | | NAKINA |
| 14 | MHAX | U.S. Dept. of the Interior, Bureau of Land Management, Helium Operations | eliminated 10/1998 | | NAKINA |
| 15 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/1982; 1/1994 | | NAKINA |
| 16 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Division of Helium Operations, Amarillo, Texas | added 10/1981; eliminated 7/1982 | | NAKINA |
| 17 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/1980; eliminated 10/1981 | | NAKINA |
| 18 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations, Amarillo, Texas | eliminated 7/1980 | | NAKINA |
| 19 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations | added 7/1971; 1/1975-1/1980 | | NAKINA |
| 20 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | 10/1966; eliminated 7/1971 | | NAKINA |
| 21 | MHAX | U.S. Dept. of the Interior, Bureau of Mines | 10/1957-7/1965 | | NAKINA |
| 22 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | added 7/1955 | | NAKINA |
| 23 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | added 7/55 | | NRHS |
| 24 | MHAX | U.S. Dept. of the Interior, Bureau of Mines | 10/57-7/65 | | NRHS |
| 25 | MHAX | U.S. Dept. of the Interior, Bureau of Mines Helium Activity | Oct-66 | | NRHS |
| 26 | MHAX | U.S. Dept. of the Interior, Bureau of Mines | Apr-70 | | NRHS |
| 27 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations | 1/75-1/80 | | NRHS |
| 28 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Operations, Amarillo, Texas | eliminated 7/80 | | NRHS |
| 29 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/80; eliminated 10/81 | | NRHS |
| 30 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Division of Helium Operations, Amarillo, Texas | added 10/81; eliminated 7/82 | | NRHS |
| 31 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | added 7/82; 1/94 | | NRHS |
| 32 | MHAX | U.S. Dept. of the Interior, Bureau of Land Management, Helium Opers | eliminated 10/98 | | NRHS |
| 33 | MHAX | U.S. Dept. of the Interior, Bureau of Mines, Helium Field Operations, Amarillo, Texas | Jul-00 | | NRHS |
| 34 | MHAX | US DEPT. OF THE INTERIOR - BUREAU OF MINES, HELIUM FIELD OPERATIONS, AMARILLO, TX | | | PWRC |
| 35 | MHAX | United States Department of the Interior Bureau of Mines Helium Field Operations | | | RSRV |
| 36 | MHAX | USDI-BUR OF MINES,DIV OF HELIUM OPE | | | SCAC4 |
| 37 | MHAY | MEHERRIN AGRICULTURAL & CHEMICAL CO | | | SCAC4 |