| 1 | OCT | Occidental Airlines (Liberia), Inc. | Callsign: Occidental, | LB | AVCODES |
| 2 | OCT | Octavia Air Ltd. | Callsign: Octavia, | GB | AVCODES |
| 3 | OCT | OCTORARO RAILWAY INC | | | PWRC |
| 4 | OCTA | OVERSEAS COAL TRANSPORT INC. | | | SCAC3 |
| 5 | OCTA | Orange County Transportation Authority | | US-CA | TRAFFIC |
| 6 | OCTB | O/C TRANSPORTATION | | | SCAC4 |
| 7 | OCTD | OCEAN TRANSPORT LTD | | | SCAC4 |
| 8 | OCTD | Orange County Transit District | | USA | TRAFFIC |
| 9 | OCTG | OCEAN CITY TRUCKING INC | | | SCAC3 |
| 10 | OCTG | O C TRUCKING | | | SCAC4 |
| 11 | OCTH | OCEANIC TRUCKING CO OF TEXAS INC | | | SCAC3 |
| 12 | OCTI | OCEAN TRUCKING | | | SCAC3 |
| 13 | OCTI | OCTAVE INTERNATIONAL HOLDINGS LTD | | | SCAC4 |
| 14 | OCTJ | OCEAN TRANSPORT LLC | | | SCAC4 |
| 15 | OCTL | Oil Creen & Titusville Lines | 1/1994-7/2005 | | NAKINA |
| 16 | OCTL | Oil Creen & Titusville Lines | 1/94-7/2000 | | NRHS |
| 17 | OCTL | OIL CREEK & TITUSVILLE LINES | | | PWRC |
| 18 | OCTL | Oil Creek and Titusville Lines | | | RSRV |
| 19 | OCTL | OIL CREEK & TITUSVILLE LINES | | | SCAC3 |
| 20 | OCTL | OIL CREEK & TITUSVILLE LINES | | | SCAC4 |
| 21 | OCTN | OCEANIC TRANSPORTATION INC | | | SCAC4 |
| 22 | OCTO | O AND C TRANSPORT LLP | | | SCAC4 |
| 23 | OCTQ | OCONNOR TRANSPORT INC | | | SCAC3 |
| 24 | OCTR | Morristown & Erie Ry., Inc., d/b/a Octoraro R.R. | eliminated 4/2007 | | NAKINA |
| 25 | OCTR | Morristown & Erie Ry., Inc., d/b/a Ontario R.R. | added 10/2003; 7/2005 | | NAKINA |
| 26 | OCTR | Octoraro Ry., Inc. | added 10/1978; 1/1980, eliminated 10/1985; 1/1994; eliminated 10/1994; 7/2000 | | NAKINA |
| 27 | OCTR | Octoraro Ry., Inc. | added 10/78; 1/80-1/94; eliminated 10/94; 7/2000 | | NRHS |
| 28 | OCTR | MORRISTOWN & ERIE RWY. CO. d/b/a OCTORARO RAILROAD | | | PWRC |
| 29 | OCTR | Octoraro Railway | | | RSRV |
| 30 | OCTR | OCTORARO RAILWAY INC | | | SCAC3 |
| 31 | OCTR | OCTORARO RAILROAD INC | | | SCAC4 |
| 32 | OCTR | OC Transpo | City: Ottawa | CDN | TRAFFIC |
| 33 | OCTU | OCEAN CONTAINERS TRADING S.L. | | E | BIC |
| 34 | OCTW | ORANGE COUNTY TOWING SERVICE INC | | | SCAC3 |
| 35 | OCTX | Octel America, Inc. | 7/2000-7/2005 (not listed) | | NAKINA |
| 36 | OCTX | Octel America, Inc. | Jul-00 | | NRHS |
| 37 | OCTX | OCTEL AMERICA INCORPORATED | | | PWRC |
| 38 | OCTX | Octel America | | | RSRV |
| 39 | OCTX | OCTEL AMERICA, INC. | | | SCAC4 |
| 40 | OCTY | ONTARIO CONTAINER TRANSPORT INC | | | SCAC4 |
