| 1 | OC | Sunshine Aviation SA | ICAO: SHS, Callsign: Sunshine, Designator OC recalled by IATA | CH | AVCODES |
| 2 | OC | Aircraft Operating Co. (Aerial Surveys) Ltd. | Callsign: Airphotos, | ZA | AVCODES |
| 3 | OC | Air California | ICAO: ACL, Callsign: Aircal, Founded in 1967. Merged into American Airlines during 1987. | USA | AVCODES |
| 4 | OC | Oriental Air Bridge Co. Ltd. | ICAO: ORC, Callsign: Oriental Bridge, IATA designator changed from O3. ICAO Designator changed to NGK. | J | AVCODES |
| 5 | OC | OLIN CORPORATION | | | PWRC |
| 6 | OC | Oregon & California Railroad | | USA | TRAFFIC |
| 7 | OC | Société du chemin de fer Orbe-Chavornay SA | | CH | VKM |
| 8 | OCA | Aserca Airlines, C.A. | IATA: R7, Callsign: Arosca, Ceased operations on 22 May 2018 | YV | AVCODES |
| 9 | OCA | Aeroservicios Carabobo C.A. Aserca | IATA: R7, | YV | AVCODES |
| 10 | OCA | Aserca Airlines | IATA: R7 | | ICAO1 |
| 11 | OCAA | ORCA CANADIAN TRANSPORT LTD | | | SCAC4 |
| 12 | OCAB | OUTSIDE CARRIER | | | SCAC4 |
| 13 | OCAC | OK COAL AND CONCRETE | | | SCAC4 |
| 14 | OCAH | OTAY CARGO | | | SCAC4 |
| 15 | OCAI | OCEAN AIRE INC | | | SCAC4 |
| 16 | OCAL | OCAL TRANSPORT CO | | | SCAC3 |
| 17 | OCAL | ONE FOUR SIX EIGHT ONE FOUR (146814 | | | SCAC4 |
| 18 | OCAM | OTG CARGO | | | SCAC4 |
| 19 | OCAP | OUTLAW CUSTOMS AND PERFORMANCE LTD | | | SCAC4 |
| 20 | OCAQ | OCEANIC LTD INC | | | SCAC3 |
| 21 | OCAR | OCEANAIR INC | | | SCAC3 |
| 22 | OCAR | OCEANAIR INC | | | SCAC4 |
| 23 | OCAS | OCEAN A/S | | | SCAC3 |
| 24 | OCAS | O C T | | | SCAC4 |
| 25 | OCAU | OCEANBOX CONTAINERS LTD | | CY | BIC |
| 26 | OCAU | OCE ANDENO, B.V. | | | SCAC3 |
| 27 | OCAY | OCEANIA TANKER CORPORATION | | | SCAC4 |
| 28 | OCBC | O C BRUMSHIRE CO | | | SCAC3 |
| 29 | OCBC | O C BRUMSHIRE CO | | | SCAC4 |
| 30 | OCBI | OCEAN BARGE INC | | | SCAC3 |
| 31 | OCBI | OCEAN BEAUTY SEAFOODS INC | | | SCAC4 |
| 32 | OCBQ | OCEAN BEACH TRF & STG CO | | | SCAC3 |
| 33 | OCBS | OCEANBRIDGE SHIPPING LTD | | | SCAC3 |
| 34 | OCBS | OCEANBRIDGE SHIPPING LTD | | | SCAC4 |
| 35 | OCBU | OCEAN BLUE FINANCE GROUP LIMITED | | HK | BIC |
| 36 | OCC | Occidental Airlines | | LB | AVCODES |
| 37 | OCC | German Forces Operations Control | | D | AVCODES |
| 38 | OCCC | O C C INC | | | SCAC3 |
| 39 | OCCC | OCEAN CARGO CARRIERS CO LLC | | | SCAC4 |
| 40 | OCCD | OCCIDENTAL SERVICES CORP | | | SCAC3 |
| 41 | OCCE | OCONNERS EXPRESS | | | SCAC3 |
| 42 | OCCE | OCONNERS EXPRESS INC | | | SCAC4 |
| 43 | OCCF | OKLAHOMA CUSTOM COURIER LLC | | | SCAC4 |
| 44 | OCCH | OVERLAND COACH INC | | | SCAC3 |
| 45 | OCCH | ON TIME MESSENGER SERVICE INC | | | SCAC4 |
| 46 | OCCI | OCCIDENTAL CARRIERS S.A. | | | SCAC3 |
| 47 | OCCI | OCCIDENTAL E N E | | | SCAC4 |
| 48 | OCCL | ORANGE COUNTY CONTAINER GROUP LLC | | | SCAC4 |
| 49 | OCCP | OLYMPIC CARRIER CORPORATION | | | SCAC3 |
| 50 | OCCP | OCEAN STAR INTERNATIONAL LOGISTICS | | | SCAC4 |
| 51 | OCCQ | OCEANIA CRUISES INC | | | SCAC4 |
| 52 | OCCR | OCEANSTAR CORPORATION | | | SCAC3 |
| 53 | OCCR | OCEAN CERAMICS LTD | | | SCAC4 |
| 54 | OCCS | OCEANIC SHIPPING CORP MONTREAUX SW | | | SCAC4 |
| 55 | OCCT | OCCIDENTAL TRANSPORTATION CO LTD | | | SCAC3 |
| 56 | OCCU | ORANGE CONTAINER LINE B.V. | | NL | BIC |
| 57 | OCCU | ATS CONTAINER LEASING S.A. | | | PWRC |
| 58 | OCCU | ATS Container Leasing SA | | | RSRV |
| 59 | OCCU | ORBIS CONTAINER SERVICE CORP., A.G. | | | SCAC3 |
| 60 | OCCV | ON CUSTOMS COURIER SERVICE INC | | | SCAC4 |
| 61 | OCCX | Occidental Chemical Corp. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 62 | OCCX | Occidental Chemical Corp. Agricultural Products | added 4/1989; eliminated 1/1992 | | NAKINA |
| 63 | OCCX | Occidental Chemical Corp. Agricultural Products Group | added 7/1988; eliminated 4/1989 | | NAKINA |
| 64 | OCCX | Occidental Chemical Agricultural Products, Inc. | added 1/1983; eliminated 7/1988 | | NAKINA |
| 65 | OCCX | Occidental Chemical Co. | added 4/1981; eliminated 1/1983 | | NAKINA |
| 66 | OCCX | Occidental Chemical Co. | added 4/81; eliminated 1/83 | | NRHS |
| 67 | OCCX | Occidental Chemical Agricultural Products, Inc. | added 1/83; eliminated 7/88 | | NRHS |
| 68 | OCCX | Occidental Chemical Corp. Agricultural Products Group | added 7/88; eliminated 4/89 | | NRHS |
| 69 | OCCX | Occidental Chemical Corp. Agricultural Products | added 4/89; eliminated 1/92 | | NRHS |
| 70 | OCCX | Occidental Chemical Corp. | added 1/92; 1/94-7/2000 | | NRHS |
| 71 | OCCX | OCCIDENTAL CHEMICAL CORP., AGRICULTURAL PRODUCTS | | | PWRC |
| 72 | OCCX | Occidental Chemical | | | RSRV |
| 73 | OCCX | OCCIDENTAL CHEMICAL CORPORATION | | | SCAC4 |
| 74 | OCCZ | OCCIDENTAL CHEMICAL CORP. | | | PWRC |
| 75 | OCDA | ONE CALL DOES IT ALL | | | SCAC4 |
| 76 | OCDG | ODECO TRADING INC | | | SCAC4 |
| 77 | OCDI | OCEAN DUCHESS INC | | | SCAC3 |
| 78 | OCDI | OLIVER CUSTOM DELIVERY LIMITED | | | SCAC4 |
| 79 | OCDN | OCCIDENTAL TOURS | | | SCAC3 |
| 80 | OCDN | OCEAN DANCER FISHING LTD | | | SCAC4 |
| 81 | OCDT | OCEANICA COMPANIA DE TRANSPORTES SA | | | SCAC3 |
| 82 | OCE | Helicocean | Callsign: Heliocean, | NC | AVCODES |
| 83 | OCE | Heliocean | | | ICAO1 |
| 84 | OCE | Oregon, California & Eastern Ry. Co. | 1/1975; added 4/1977; 1/1980; eliminated 4/1992; 1/1994 | | NAKINA |
| 85 | OCE | Oregon, California & Eastern Ry. Co. | 1/75-1/80; eliminated 4/92; 1/94 | | NRHS |
| 86 | OCE | RETIRED 06-05-92 (603) ATP [OREGON, CALIFORNIA & EASTERN RY.] | | | PWRC |
| 87 | OCE | Oregon, California and Eastern Railway | | | RSRV |
| 88 | OCEA | OCEANBULK LINE | | | SCAC3 |
| 89 | OCEANC | Ocean County Department of Transportation Services | City: Toms River, NJ | US-NJ | TRAFFIC |
| 90 | OCEB | OCEAN BEACH TRANSFER & STORAGE, INC | | | SCAC3 |
| 91 | OCEC | OCEAN CITY EXPRESS CO INC | | | SCAC4 |
| 92 | OCEE | OCOEE RIVER TRANSPORT INC | | | SCAC4 |
| 93 | OCEL | OCEAN EXPRESS LINE INC | | | SCAC3 |
| 94 | OCEL | ODIS CRANE & EQUIPMENT LLC | | | SCAC4 |
| 95 | OCEN | OCEAN SPRINGS TRANSFER & STORAGE IN | | | SCAC3 |
| 96 | OCEN | OCEAN SPRINGS TRANSFER & STORAGE IN | | | SCAC4 |
| 97 | OCEO | OCEANO SHIPPING CO INC | | | SCAC4 |
| 98 | OCEQ | OCEAN TRANSPORT | | | SCAC4 |
| 99 | OCET | OCEAN TERMINALS, INC | | | SCAC3 |
| 100 | OCET | OCEAN TERMINALS INC | | | SCAC4 |
