| 1 | OE | Cairo Air Transport Company (Cairo Aviation) | ICAO: CCE, Designator OE recalled by IATA | ET | AVCODES |
| 2 | OE | Air Omega Luftverkehrsgesellschaft mbH | ICAO: AOW, Callsign: Warlock, Designator OE recalled by IATA | D | AVCODES |
| 3 | OE | Express Air Services (Channel Islands) Ltd. | IATA designator changed to LS | GB | AVCODES |
| 4 | OE | Asia Overnight Express Corporation | ICAO: AOT, Callsign: Asia Overnight, IATA Prefix: 918, | RP | AVCODES |
| 5 | OE | Westair Commuter Airlines, Inc. / United Express | ICAO: SDU, Designator OE recalled by IATA | USA | AVCODES |
| 6 | OE | Out-Island Airways Ltd. | | GB | AVCODES |
| 7 | OE | Bedarfsflugunternehmen Dr. L. Polsterer | ICAO: OPV, Callsign: Polsterer, | A | AVCODES |
| 8 | OE | Lauda Air Luftfahrt AG | Callsign: Lauda Air, IATA Designator changed to OE | A | AVCODES |
| 9 | OE | Yeongnam Air Co. Ltd. | ICAO: ONA, Callsign: Yeongnam Air, Founded in 2008. Commenced operations on 25 July 2008. Ceased operations in December 2008. | ROK | AVCODES |
| 10 | OE | LaudaMotion GmbH | ICAO: LDM, Callsign: Expert, Ceased operations on 31 October 2020 as operations transferred to Lauda Europe. Prevoiusly Niki. Sold to LaudaMotion on 23 January 2018. | A | AVCODES |
| 11 | OE | Fly One Airlines S.r.l. | ICAO: FOE, Callsign: First Eagle, | RO | AVCODES |
| 12 | OE | Oregon Electric Ry. Co. (Spokane, Portland & Seattle Ry. Co.) | 10/1966 | | NAKINA |
| 13 | OE | Oregon Electric Ry. Co. | 1/1975-1/1980 | | NAKINA |
| 14 | OE | Oregon Electric Ry. | 1/1950-7/1965 | | NAKINA |
| 15 | OE | The Ohio Electric Ry. Co. | 8/1920 | | NAKINA |
| 16 | OE | Oregon Electric Ry. | 1/52-7/65 | | NRHS |
| 17 | OE | Oregon Electric Ry. Co. (Spokane, Portland & Seattle Ry. Co.) | Oct-66 | | NRHS |
| 18 | OE | Oregon Electric Ry. Co. | 1/75-1/80 | | NRHS |
| 19 | OE | *OHIO ELECTRIC RAILWAY CO. | | | PWRC |
| 20 | OE | *(BN) RETIRED 10-12-92 ATP [SPOKANE, PORTLAND & SEATTLE RWY. CO.; OREGON ELECTRIC RWY.(SPS)] | | | PWRC |
| 21 | OE | *ORION EXPRESS | | | PWRC |
| 22 | OEA | Orient Thai Airlines | IATA: OX, Callsign: Orient Thai, Designator OX* recalled by IATA | T | AVCODES |
| 23 | OEA | Orient Thai Airlines | IATA: OX, Callsign: Orient Thai, IATA designator changed to OX. Designator OX* reinstated by IATA | T | AVCODES |
| 24 | OEA | Orient Thai Airlines Company Limited | IATA: OX, Callsign: Orient Thai, IATA Prefix: 578, IATA designator changed from OX*. Designator OX* reinstated by IATA | T | AVCODES |
| 25 | OEA | Orient Thai Airlines | IATA: OX | | ICAO1 |
| 26 | OEBA | OYSTER BROTHERS AGWAY | | | SCAC3 |
| 27 | OEBA | OPERATION FORESTIER MARTIN DUBE &SO | | | SCAC4 |
| 28 | OEBB | Oensingen-Balsthal-Bahn | | CH | TRAFFIC |
| 29 | OEBB | Oensingen-Balsthal-Bahn | | CH | VKM |
| 30 | OEBN | OEBIN | | | SCAC4 |
| 31 | OEBU | OSTERREICHISCHE BUNDESBAHNEN | | | SCAC3 |
| 32 | OEBU | OSTERREICHISCHE | | | SCAC4 |
| 33 | OEC | Christophorus Flugrettungsverein | | | ICAO1 |
| 34 | OECC | OEC FREIGHT CHICAGO INC | | | SCAC4 |
| 35 | OECF | OEC FREIGHT WORLDWIDE CO LTD | | | SCAC4 |
| 36 | OECM | OEC (MTL) INC | | | SCAC4 |
| 37 | OECN | ONE FOUR EIGHT EIGHT ZERO SEVEN (14 | | | SCAC4 |
| 38 | OECO | OVERSEAS EXPORT CRATING CO INC | | | SCAC3 |
| 39 | OECP | OMEGA ENERGY CORP | | | SCAC4 |
| 40 | OECR | OPTRIM ENERGY CORPORATION | | | SCAC4 |
| 41 | OECX | Oldbury Electro-Chemical Co. | 7/1937-7/1954; 10/1957 (not listed); eliminated 10/1957 | | NAKINA |
| 42 | OECX | Oldbury Electro-Chemical Co. | 4/38-10/57; eliminated 10/57 | | NRHS |
| 43 | OECX | OLDBURY ELECTRO-CHEMICAL CO. | | | PWRC |
| 44 | OECY | OVERLAND ENTERPRISE CO | | | SCAC4 |
| 45 | OED | Orion Air Charter | Callsign: Orion Charter, | ZA | AVCODES |
| 46 | OED | Orion Air Charter | | | ICAO1 |
| 47 | OEDS | ORIENT EXPRESS DELIVERY SERVICE INC | | | SCAC3 |
| 48 | OEDX | Ohio Edison Co. | added 4/1958; 4/1961-1/1980; eliminated 5/1983 | | NAKINA |
| 49 | OEDX | Ohio Edison Co. | 4/61-1/80; eliminated 5/83 | | NRHS |
| 50 | OEDX | OHIO EDISON COMPANY | | | PWRC |
| 51 | OEDX | Ohio Edison | | | RSRV |
| 52 | OEDX | OHIO EDISON CO | | | SCAC3 |
| 53 | OEEI | OLD EPHRAIM EXPRESS INC | | | SCAC4 |
| 54 | OEF | Oberhessische Eisenbahnfreunde eV | Lollar | D | privat-bahn.de |
| 55 | OEF | Oberhessische Eisenbahnfreunde e.V. | | DE | VKM |
| 56 | OEFC | OVERTIME EXPRESS FREIGHT CO | | | SCAC3 |
| 57 | OEFC | OCEANLAND DISTRIBUTION SERVICES LTD | | | SCAC4 |
| 58 | OEFE | OMADA FURNITURE INC | | | SCAC4 |
| 59 | OEFI | ONE FIVE ONE ZERO NINE EIGHT EIGHT | | | SCAC4 |
| 60 | OEFT | ONE EIGHT FOUR THREE-SEVEN FOUR SEV | | | SCAC3 |
| 61 | OEG | Orient Eagle Airways | IATA: 4R, Callsign: Orienteagle, Ceased operations | KZ | AVCODES |
| 62 | OEG | Oberrheinische Eisenbahn-Gesellschaft AG | Mannheim | D | privat-bahn.de |
| 63 | OEG | Oberrheinische Eisenbahngesellschaft (Mannheim) | City: Mannheim | D | TRAFFIC |
| 64 | OEGI | OCTANE EXPRESS GROUP INC | | | SCAC4 |
| 65 | OEGIE | Stiftung BSW, Oberhessische Eisenbahnfreunde Gießen | | DE | VKM |
| 66 | OEGL | OPEL EYE GROUP LTD | | | SCAC4 |
| 67 | OEGU | OEG OFFSHORE GROUP LIMITED | | SGP | BIC |
| 68 | OEGU | OEG OFFSHORE PTE LTD | | | SCAC4 |
| 69 | OEHB | OEHLERT BROS INC | | | SCAC4 |
| 70 | OEHL | OEHLKE TRUCK LINE | | | SCAC3 |
| 71 | OEHM | OEHME CARRIER CORPORATION | | | SCAC4 |
| 72 | OEHQ | OEHRLEIN TRUCKING | | | SCAC3 |
| 73 | OEHR | OEHRLEIN SALT SALES | | | SCAC3 |
| 74 | OEIB | O E I BUSINESS FORMS | | | SCAC3 |
| 75 | OEIB | OEHLERKING HAULING | | | SCAC4 |
| 76 | OEIC | OWENS EXPRESS INC | | | SCAC3 |
| 77 | OEID | ONDAR EXPRESS INC | | | SCAC4 |
| 78 | OEIK | ONYX ENTERPRISES INC | | | SCAC4 |
| 79 | OEIN | OCEAN EXPRESS INC | | | SCAC4 |
| 80 | OEIP | ONTIME EXPRESS INC | | | SCAC4 |
| 81 | OEL | Ontario Express Ltd. | IATA: 9X, Callsign: Partner, Canadian Partner | CDN | AVCODES |
| 82 | OELD | OAHU EXPRESS LTD | | | SCAC4 |
| 83 | OELE | ORLANDO ENTERPRISE LLC | | | SCAC4 |
| 84 | OELL | OTTOMAN ENTERPRISES LLC | | | SCAC4 |
| 85 | OELN | ONTIME EXPRESS LINE INC | | | SCAC4 |
| 86 | OELX | O.E. Linsin, Inc. | 7/1935-4/1970; eliminated 4/1974 | | NAKINA |
| 87 | OELX | O.E. Linsin, Inc. | 4/38-4/70; eliminated 4/74 | | NRHS |
| 88 | OELX | O.E. LINSIN, INC. | | | PWRC |
| 89 | OELX | LINSIN INC, OE | | | SCAC3 |
| 90 | OENI | OSAGE ENTERPRISES INC | | | SCAC3 |
| 91 | OENI | OSAGE ENTERPRISES INC | | | SCAC4 |
| 92 | OENS | OWENS TRANSPORTATION LLC | | | SCAC4 |
| 93 | OEOE | OFFICE ENVIROMENTS OF N E | | | SCAC4 |
| 94 | OEOT | ONE EIGHT ONE EIGHT SIX THREE ZERO | | | SCAC4 |
| 95 | OEPF | OLD EL PASO (DIV OF | | | SCAC4 |
| 96 | OEPOST | Österreichische Bundespost: Postbus | | A | TRAFFIC |
| 97 | OEPT | OIL EXPRESS PETROLEUM TRANSPORT INC | | | SCAC3 |
| 98 | OEQN | OGILVY EQUESTRIAN | | | SCAC4 |
| 99 | OEQT | ORGANIC EQUIPMENT TECHNOLOGY | | | SCAC4 |
| 100 | OER | OREGON ELECTRIC RAILWAY | | | PWRC |
