| 1 | HCO | Harco Air Services | Callsign: Harco Air, | WAN | AVCODES |
| 2 | HCO | HOWE COAL (OKLAHOMA) | | | PWRC |
| 3 | HCOC | HALLS CONCRETE | | | SCAC4 |
| 4 | HCOD | HEARTLAND COOP | | | SCAC4 |
| 5 | HCOF | HILL CITY OIL COMPANY INC | | | SCAC4 |
| 6 | HCOJ | HUBZONE CORPORATION | | | SCAC4 |
| 7 | HCOK | HALLMARK CORP | | | SCAC4 |
| 8 | HCOO | HEETCO INC | | | SCAC4 |
| 9 | HCOR | HARRIS CORPORATION | | | SCAC4 |
| 10 | HCOS | HANKS CONSTRUCTION | | | SCAC4 |
| 11 | HCOU | CONICAL GMBH | | D | BIC |
| 12 | HCOU | CONICAL CONTAINER INDUSTRIE | | | SCAC3 |
| 13 | HCOU | CONICAL CONTAINER INDUSTRIE CONSULT | | | SCAC4 |
| 14 | HCOW | HUNT CRUDE OIL SUPPLY COMPANY | | | SCAC4 |
| 15 | HCOY | HOLMFIELD COLONY FARMS | | | SCAC4 |
