| Known As / Full Name | URL |
|---|---|
| OAG / OAG Worldwide. | www.oag.com |
| OAS Helicopters / Odengene Air Shuttle Services Limited | www.oas-helicopters.org |
| Oasis Flight / Oasis Flight Ltd | www.oasisflight.co.uk |
| OCL Barbados / OCL (Barbados) Ltd. | flyonecaribbean.com |
| Odessa Aircraft Plant / Odessa Aircraft Plant | www.avirs.ua |
| OFD / Ostfriesischer-Flug-Dienst GmbH | www.fliegofd.de |
| Offshore Helicopter Services UK Ltd. / Offshore Helicopter Services UK Limited | ultimate-aviation.net/service/who-we-are/ |
| Ohio State University Flight Education Division / Ohio State University Flight Education Division | aviation.osu.edu |
| OK Business Aircraft / OK Business Aircraft | www.ok-aviation.cz/en |
| Okay Airways / Okay Airways Company Limited | www.okair.net |
| Oklahoma State University / Oklahoma State University | go.okstate.edu |
| Old Dominion Freight LT Lines / Old Dominion Freight LT Lines, Inc. | www.odfl.com |
| Olympic Air / Olympic Air | www.olympicair.com |
| Olympic Broadcasting Services / Olympic Broadcasting Services | www.obs.es |
| Olympus Airways / Olympus Airways | www.olympusairways.gr |
| Oman Air / Oman Air | www.oman-air.com |
| Omega Aerial Refueling Services / Omega Aerial Refueling Services, Inc. | www.omegaairrefueling.com |
| Omni - Aviacao E Tecnologia / Omni - Aviacao E Tecnologia, Lda | www.omni.pt |
| Omni Air Express / Omni Air International, Inc. d/b/a Omni Air Express | www.oai.aero |
| Omni Air Transport / Omni Air Transport, LLC | www.omniairtransport.com |
| Omni Aviation Training Center / Omni Aviation Training Center | www.oatc.pt |
| Omni Taxi Aereo / Omni Taxi Aereo S.A. | www.omnibrasil.com.br |
| Omni-blu Aviation / Omni-blu Aviation Limited | omniblu.com |
| One Air / Grupo One Air Aviacion, S.L. | www.grupooneair.com |
| One Air / One Air Limited | www.aironeaviation.com |
| ONE Aviation / ONE Aviation Corporation | www.eclipseaviation.com |
| On-Track Aviation / On-Track Aviation Ltd. | www.ontrackaviation.com |
| Open Flight / Open Flight | www.openflight.fr |
| Opera Jet / Opera Jet s.r.o. | www.operajet.sk |
| Oriental Air Bridge / Oriental Air Bridge Co. Ltd. | www.orc-air.co.jp |
| Originair / Originair | www.originair.co.nz |
| Orion Airways / Orion Airways | flyorionairways.com |
| Orion Airways / Orion Airways | flyorionairways.com |
| Ornge Air / Ornge Global Air Inc | www.ornge.ca |
| Ortac AOC Ltd. / Ortac AOC Ltd. | www.ortac-ops.com |
| Oryx Jet / Oryx Jet Ltd | www.oryxjet.com |
| Oslo Politidistrikt, Helikoptertjenesten / Oslo Politidistrikt, Helikoptertjenesten | www.politi.no/oslo |
| OSM Aviation Academy / OSM Aviation Academy AB | www.osmaviationacademy.com |
| Osterman Helicopter / Osterman Helicopter | www.ostermanhelicopter.se |
| Oulun Tilauslento / Oulun Tilauslento Oy | www.ouluntilauslento.fi |
| Overland Airways / Overland Airways Limited | www.overlandairways.com |
| Owenair / Owenair (Pty) Ltd. | owenair.co.za |
| Owyhee Air Research / Owyhee Air Research, LLC | www.owyheeair.com |
| Oxford Aviation Academy / Oxford Aviation Academy | www.caeoaa.com |
| Oya Vendée Hélicoptères S.A.S. / Oya Vendée Hélicoptères S.A.S. | www.oya-helico.fr |
| Oyonnair / Oyonnair | www.oyonnair.com |