| 1 | HEP | Heliopolis Airline | Callsign: Heliopolis, Name changed to Flash Airlines (7K/FSH) during 2000. | ET | AVCODES |
| 2 | HEP | Oslo Politidistrikt, Helikoptertjenesten | Callsign: Helipolice, | N | AVCODES |
| 3 | HEPK | HELPACE | | | SCAC4 |
| 4 | HEPP | HEPP TRUCK SERVICE, INC | | | SCAC1 |
| 5 | HEPP | HEPP, DAVID W TRUCKING INC | | | SCAC4 |
| 6 | HEPX | Hydro One | added 4/2001; 7/2005 | | NAKINA |
| 7 | HEPX | Ontario Hydro | added 7/1975; 1/1980-7/2000; eliminated 4/2001 | | NAKINA |
| 8 | HEPX | Hydro-Electric Power Commission of Ontario | 1/1952-1/1975; eliminated 7/1975 | | NAKINA |
| 9 | HEPX | Headley Emulsified Products Co. | 7/1930-7/1932 | | NAKINA |
| 10 | HEPX | Hydro-Electric Power Commission of Ontario | 1/52-1/75; eliminated 7/75 | | NRHS |
| 11 | HEPX | Ontario Hydro | added 7/75; 1/80-7/2000; eliminated 4/2001 | | NRHS |
| 12 | HEPX | Hydro One | added 4/2001 | | NRHS |
| 13 | HEPX | *HEADLEY EMULSIFIED PRODUCTS CO. | | | PWRC |
| 14 | HEPX | +ONTARIO HYDRO (HYDRO ONE) | | | PWRC |
| 15 | HEPX | Ontario Hydro (Hydro One) | | | RSRV |
| 16 | HEPX | HYDRO-ELECTRIC POWER COMMISSION OF | | | SCAC4 |
