| 1 | OMA | Oman Air | Callsign: Khanjar, ICAO callsign changed from Oman Air | OM | AVCODES |
| 2 | OMA | Oman Air | Callsign: Oman Air, ICAO callsign changed to Khanjar | OM | AVCODES |
| 3 | OMA | Oman Air | IATA: WY, Callsign: Oman Air, IATA Prefix: 910, ICAO callsign changed from Khanjar | OM | AVCODES |
| 4 | OMA | Ontario Metro Airlines Ltd. | Callsign: Ontario Metro, | CDN | AVCODES |
| 5 | OMA | Oman Air | IATA: WY | | ICAO1 |
| 6 | OMA | Oman Air | | OM | TRAFFIC |
| 7 | OMAB | OLIVARES, MARIO ALBERTO | | | SCAC4 |
| 8 | OMAE | OMA ENTERTAINMENT, INC | | | SCAC4 |
| 9 | OMAK | ONCUE MARKETING LLC | | | SCAC4 |
| 10 | OMAO | OMEGA MARITIME INC | | | SCAC4 |
| 11 | OMAR | OMARA MOVING & STORAGE INC | | | SCAC3 |
| 12 | OMAR | OMARA MOVING & STORAGE INC | | | SCAC4 |
| 13 | OMAS | OASIS MOVING & STORAGE | | | SCAC4 |
| 14 | OMAT | OMA TRUCKING INC | | | SCAC4 |
| 15 | OMAT | Metro Area Transit | City: Omaha (NE) | USA | TRAFFIC |
| 16 | OMAU | OMNI TANKER PTY LTD | | AUS | BIC |
| 17 | OMAU | OCEAN MARINE LINE | | | SCAC3 |
| 18 | OMAX | Omaha Public Power District | added 1/1978; 1/1980-7/2005 | | NAKINA |
| 19 | OMAX | Omaha Public Power District | added 1/78; 1/80-7/2000 | | NRHS |
| 20 | OMAX | OMAHA PUBLIC POWER DISTRICT | | | PWRC |
| 21 | OMAX | Omaha Public Power District | | | RSRV |
| 22 | OMAX | OMAHA PUBLIC POWER DISTRICT | | | SCAC4 |
| 23 | OMAY | ORTH-MAYFLOWER | | | SCAC3 |
