| 1 | OMI | Omni Taxi Aereo S.A. | Callsign: Omni Air, | BR | AVCODES |
| 2 | OMI | Omi Railroad Co., Ltd. | Subsidiary of the Seibu Railway Co. Ltd. | J | TRAFFIC |
| 3 | OMIA | OIL MAN INC, THE | | | SCAC4 |
| 4 | OMIC | OMI CORP | | | SCAC3 |
| 5 | OMID | Ontario Midland R.R. Corp. | added 1/1980; 1/1980-7/2000; eliminated 4/2005; 7/2005 | | NAKINA |
| 6 | OMID | Ontario Midland R.R. Corp. | added 1/80; 1/80-7/2000 | | NRHS |
| 7 | OMID | ONTARIO MIDLAND RAILROAD CORP. | | | PWRC |
| 8 | OMID | Ontario Midland Railroad | | | RSRV |
| 9 | OMID | ONTARIO MIDLAND RAILROAD CORPORATIO | | | SCAC3 |
| 10 | OMID | Ontario Midland Railroad Corporation | | CDN | TRAFFIC |
| 11 | OMIE | OPEN MILE INC | | | SCAC4 |
| 12 | OMIH | ORITT, MICHAEL | | | SCAC4 |
| 13 | OMIL | OMI PETROLINK CORP | | | SCAC3 |
| 14 | OMIL | OMI PETROLINK CORP | | | SCAC4 |
| 15 | OMIQ | OCEANVIEW-MERCED-INGLESIDE TRUCKING | | | SCAC3 |
| 16 | OMIQ | OMEGA MANAGEMENT INC | | | SCAC4 |
| 17 | OMIR | OMI TRANSPORTATION INC | | | SCAC3 |
| 18 | OMIR | OMI TRANSPORTATION INC | | | SCAC4 |
| 19 | OMIS | OMNI SOURCE CORP | | | SCAC3 |
| 20 | OMIS | OMNISOURCE TRANSPORT LLC | | | SCAC4 |
| 21 | OMIT | O M I TRANSPORTATION SERVICES INC | | | SCAC3 |
