| 1 | OPC | Krystel Air Charter Ltd. | Callsign: Optic, | GB | AVCODES |
| 2 | OPC | Krystel Air Charter | | | ICAO1 |
| 3 | OPCC | ONYX PAVING COMPANY INC | | | SCAC4 |
| 4 | OPCI | OPTIMO CONSOLIDATORS INTERNATIONAL | | | SCAC4 |
| 5 | OPCM | OSSIAN PACKING COMPANY | | | SCAC4 |
| 6 | OPCO | OWENS PLATING CO | | | SCAC3 |
| 7 | OPCO | OPSCO ENERGY INDUSTRIES USA LIMITED | | | SCAC4 |
| 8 | OPCR | OPC TRUCKING | | | SCAC4 |
| 9 | OPCS | OPTION COURIER SERVICES INC | | | SCAC3 |
| 10 | OPCU | O P D R CANARIAS | | | SCAC4 |
| 11 | OPCX | General Electric Railcar Services Corp. | added 7/1987; eliminated 1/1988 | | NAKINA |
| 12 | OPCX | Permanente Cement Co. | added 7/1959; 4/1961; eliminated 10/1961 | | NAKINA |
| 13 | OPCX | The Olympic Portland Cement Co., Ltd. | added 4/1954; 7/1954-10/1957; eliminated 7/1959 | | NAKINA |
| 14 | OPCX | Fruit Growers Express Co. (reporting marks for Omaha Packing Co.) | 7/1937-1/1950 | | NAKINA |
| 15 | OPCX | Omaha Packing Co. (National Car Co.) | Apr-38 | | NRHS |
| 16 | OPCX | The Olympic Portland Cement Co., Ltd. | added 4/54; 10/57; eliminated 7/59 | | NRHS |
| 17 | OPCX | Permanente Cement Co. | added 7/59; 4/61 | | NRHS |
| 18 | OPCX | General Electric Railcar Services Corp. | added 7/87; eliminated 1/88 | | NRHS |
| 19 | OPCX | *OMAHA PACKING CO. (FRUIT GROWERS EXPRESS) | | | PWRC |
| 20 | OPCX | *PERMANENTE CEMENT CO. [OLYMPIC PORTLAND CEMENT CO. LTD.] | | | PWRC |
| 21 | OPCX | *GENERAL ELECTRIC RAILCAR SERVICES CORP. | | | PWRC |
| 22 | OPCY | OMNI PACIFIC COMPANY INC | | | SCAC4 |
