| 1 | OPE | Société 3 S Aviation (Aerope) | Callsign: Pontoisair, | F | AVCODES |
| 2 | OPE | Oregon Pacific and Eastern Ry. Co. | 1/1975-1/1980; eliminated 1/1994; 1/1994 (not listed); eliminated 4/1995; 7/2000-7/2005 | | NAKINA |
| 3 | OPE | Oregon Pacific and Eastern Ry. Co. | 1/75-1/80; eliminated 1/94; eliminated 4/95; 7/2000 | | NRHS |
| 4 | OPE | OREGON, PACIFIC & EASTERN RAILWAY COMPANY | | | PWRC |
| 5 | OPE | Oregon, Pacific and Eastern Railway | | | RSRV |
| 6 | OPE | OREGON PACIFIC & EASTERN RAILWAY CO | | | SCAC4 |
| 7 | OPEG | OREGON, PACIFIC & EASTERN RAILWAY COMPANY | | | PWRC |
| 8 | OPEI | OLIVER PIPE & EQUIPMENT INC | | | SCAC3 |
| 9 | OPEL | OPTIMISTIC ENTERPRISES LTD | | | SCAC3 |
| 10 | OPEL | | | D | TRAFFIC |
| 11 | OPEN | OPEN WINDOW BAKERY LIMITED | | | SCAC4 |
| 12 | OPEP | ORLY PLASTIC ENTERPRISES | | | SCAC4 |
