| 1 | OF | Transports et Travaux Aériens de Madagascar | ICAO: TML, Callsign: Tam Airline, | RM | AVCODES |
| 2 | OF | British Aircraft Corp. (BAC) (Filton Division) | | GB | AVCODES |
| 3 | OF | Air Finland Ltd. | ICAO: FIF, Callsign: Air Finland, Ceased operations and declared bankrupt on 26 June 2012. | FIN | AVCODES |
| 4 | OF | Overland Airways Limited | ICAO: OLA, Callsign: Overland, Commenced operations on 26 November 2003. IATA designator changed from OJ. | WAN | AVCODES |
| 5 | OFA | Helitaxi Ofavi, S.A. de C.V. | Callsign: Ofavi, | MEX | AVCODES |
| 6 | OFA | Helitaxi Ofavi | | | ICAO1 |
| 7 | OFAF | OUTBACK FUEL AND FEED LLC | | | SCAC4 |
| 8 | OFAH | OBERG FARMS | | | SCAC4 |
| 9 | OFAL | OFALLON GAS CO OF ST CHARLES COUNTY | | | SCAC3 |
| 10 | OFAM | OBERLE FARMS | | | SCAC4 |
| 11 | OFAS | OAHU FREIGHT ASSOCIATION | | | SCAC3 |
| 12 | OFBI | OMNI FREIGHT BROKERS INC | | | SCAC4 |
| 13 | OFBK | OSMAR FREIGHT BROKERS | | | SCAC4 |
| 14 | OFCC | OFC CORPORATION | | | SCAC4 |
| 15 | OFCL | ONE FOUR SIX EIGHT ONE FOUR (146814 | | | SCAC3 |
| 16 | OFCP | ORNELAS FONTES, CRISPINA | | | SCAC4 |
| 17 | OFCS | OFFERLE COOPERATIVE & SUPPLY CO | | | SCAC3 |
| 18 | OFCS | ONEIDA FREIGHT CARRIERS INC | | | SCAC4 |
| 19 | OFCT | OVERLAND FREIGHT CORPORATION | | | SCAC4 |
| 20 | OFCW | OLDENDORFF CARRIERS | | | SCAC4 |
| 21 | OFCX | Residco | added 7/1987; 1/1994-7/2000; eliminated 10/2004; 7/2005 (not listed); added 7/2008 | | NAKINA |
| 22 | OFCX | Ortner Freight Car Co. | added 10/1967; 4/1970-1/1980; eliminated 7/1987 | | NAKINA |
| 23 | OFCX | Ortner Freight Car Co. | added 10/67; 4/70-1/80; eliminated 7/87 | | NRHS |
| 24 | OFCX | Residco | added 7/87; 1/94-7/2000 | | NRHS |
| 25 | OFCX | *ORTNER FREIGHT CAR CO. | | | PWRC |
| 26 | OFCX | +RESIDCO | | | PWRC |
| 27 | OFCX | Ortner Freight Car | | | RSRV |
| 28 | OFCX | RESIDCO | | | SCAC4 |
| 29 | OFDC | OLSON, FRED CO INC | | | SCAC3 |
| 30 | OFDC | OFISDECO | | | SCAC4 |
| 31 | OFDL | OSBORN & ASSOCIATES OF FOND DU LAC | | | SCAC4 |
| 32 | OFDT | OILFIELD TRUCKING & TRANSPORTATION | | | SCAC3 |
| 33 | OFDT | OMSTEAD FOODS LTD | | | SCAC4 |
| 34 | OFEC | OVERLAND SYSTEMS INC | | | SCAC4 |
| 35 | OFEG | ONE FOUR EIGHT SEVEN FIVE THREE FOU | | | SCAC4 |
| 36 | OFEI | ONE FIVE EIGHT NINE SIX TWO ONE (15 | | | SCAC4 |
| 37 | OFEN | OFFEN INC | | | SCAC3 |
| 38 | OFER | ONE FOUR EIGHT THREE FOUR NINE TWO | | | SCAC4 |
| 39 | OFES | ONE FOUR EIGHT SEVEN FIVE | | | SCAC4 |
| 40 | OFET | ONE FOUR EIGHT TWO SEVEN FOUR (1482 | | | SCAC4 |
| 41 | OFF | Challenge International Airlines | Callsign: Challenge Air, | USA | AVCODES |
| 42 | OFF | Challenge International Airlines | | | ICAO1 |
| 43 | OFFC | OFFSHORE CRANE & SERVICE COMPANY, INC | | | SCAC3 |
| 44 | OFFD | OFF DOCK UNLIMITED | | | SCAC3 |
| 45 | OFFH | OFFENHEISER INC | | | SCAC4 |
| 46 | OFFI | OPPORTUNITY FAST FREIGHT INC | | | SCAC3 |
| 47 | OFFK | ONE FIVE FIVE SIX EIGHT FIVE FOUR ( | | | SCAC4 |
| 48 | OFFL | OFFICIAL FAST FREIGHT LLC | | | SCAC4 |
| 49 | OFFM | OFFICE MOVERS INC | | | SCAC3 |
| 50 | OFFM | OFFICE MOVERS INC | | | SCAC4 |
| 51 | OFFR | OHIO FAST FREIGHT, INC | | | SCAC3 |
| 52 | OFFR | ONE FOUR FIVE FIVE FOUR NINE TWO (1 | | | SCAC4 |
| 53 | OFFT | OFFMOR TRUCKING INC | | | SCAC4 |
| 54 | OFFU | CARU CONTAINERS BV | | NL | BIC |
| 55 | OFFU | CONTAINER COMPANY AMSTERDAM BV | | | SCAC4 |
| 56 | OFFV | ONE FIVE FIVE THREE SIX SIX NINE (1 | | | SCAC4 |
| 57 | OFFY | OLD FRONTIER FAMILY INC | | | SCAC4 |
| 58 | OFGC | OSKALOOSA FEED & GRAIN CO | | | SCAC3 |
| 59 | OFGX | The Osage Gasoline Corp. | 7/1923 | | NAKINA |
| 60 | OFGX | OSAGE GASOLINE CORP. | | | PWRC |
| 61 | OFII | OVERSEAS FINANCIAL INSTITUTE INC | | | SCAC4 |
| 62 | OFIN | OMEGA FREIGHT INC | | | SCAC3 |
| 63 | OFIO | OWENS FUELS INC OF WELLINGTON | | | SCAC4 |
| 64 | OFIQ | OVERNIGHT FREIGHT INC | | | SCAC4 |
| 65 | OFIT | OVERLAND FREIGHT INTERNATIONAL(OFI) | | | SCAC4 |
| 66 | OFIX | Olie Fabrieken Institute (Java Coconut Oil Co., Ltd. of New York) | 8/1920-7/1923 | | NAKINA |
| 67 | OFIX | JAVA COCONUT OIL CO. LTD. OR NEW YORK [OLIE FABRIEKEN INSTITUTE] | | | PWRC |
| 68 | OFJS | OHARA, F J & SONS INC | | | SCAC4 |
| 69 | OFK | OFEK | | IL | AVCODES |
| 70 | OFKX | Witco Chemical Corp. | added 1/1969; 4/1970-1/1975 | | NAKINA |
| 71 | OFKX | Witco Chemical Co., Inc. | added 1/1967; eliminated 1/1969 | | NAKINA |
| 72 | OFKX | Koch Tank Line, Inc. | 7/1937-10/1966; eliminated 1/1967 | | NAKINA |
| 73 | OFKX | Otto Koch | 7/1930 | | NAKINA |
| 74 | OFKX | Koch Tank Line | 7/1932-7/1935 | | NAKINA |
| 75 | OFKX | Koch Tank Line, Inc. | 4/38-10/66; eliminated 1/67 | | NRHS |
| 76 | OFKX | Witco Chemical Co., Inc. | added 1/67; eliminated 1/69 | | NRHS |
| 77 | OFKX | Witco Chemical Corp. | added 1/69; 4/70-1/75 | | NRHS |
| 78 | OFKX | WITCO CHEMICAL [KOCH TANK LINE; OTTO KOCH] | | | PWRC |
| 79 | OFKX | KOCH TANK LINE | | | SCAC3 |
| 80 | OFL | Open Flight | Callsign: Open Flight, | F | AVCODES |
| 81 | OFLA | OPTIMAL FREIGHT LLC | | | SCAC4 |
| 82 | OFLC | OSG FREIGHT LINES LLC | | | SCAC4 |
| 83 | OFLD | OTTOR FREIGHTWAYS LIMITED | | | SCAC3 |
| 84 | OFLL | OVERLAND FREIGHT LINES LTD | | | SCAC3 |
| 85 | OFLM | OILFIELD MAINTENANCE COMPANY | | | SCAC3 |
| 86 | OFLN | OSCAR FREIGHT LINE | | | SCAC3 |
| 87 | OFLW | OVERFLOW ULTRA LOGISTICS | | | SCAC4 |
| 88 | OFM | Oasis Flight Malta Ltd | | M | AVCODES |
| 89 | OFMK | OC FLOCK MANAGEMENT | | | SCAC4 |
| 90 | OFMO | OLSEN & FIELDING MOVING SERVICES | | | SCAC3 |
| 91 | OFMO | OLSEN & FIELDING MOVING SERVICES | | | SCAC4 |
| 92 | OFMS | OTT, FRED M & SONS INC | | | SCAC3 |
| 93 | OFNA | ONE FIVE FIVE FIVE NINE THREE EIGHT | | | SCAC4 |
| 94 | OFNC | ONE FOUR NINE SEVEN ONE THREE (1497 | | | SCAC4 |
| 95 | OFNE | ONE FOUR NINE EIGHT TWO ONE ONE (14 | | | SCAC4 |
| 96 | OFNL | ONE FIVE NINE ZERO EIGHT TWO EIGHT | | | SCAC4 |
| 97 | OFNP | OFFEN PETROLEUM INC | | | SCAC4 |
| 98 | OFNR | ONE ELEVEN FARMS & NURSERIES | | | SCAC4 |
| 99 | OFNS | ONE TWO THREE FIVE FOUR NINE SIX (1 | | | SCAC4 |
| 100 | OFOA | ONE FOUR ONE THREE THREE | | | SCAC4 |
