| 2801 | OPTI | OBARTO PRODUCE INC | | | SCAC3 |
| 2802 | OPTI | OPTIMISTIC ENTERPRISES (LUMBER DIVI | | | SCAC4 |
| 2803 | OPTIS | OPTISPED, a.s. | | SK | VKM |
| 2804 | OPTL | O/P TRANSPORTATION LTD INC | | | SCAC3 |
| 2805 | OPTM | OPTIMUS TRANSPORT INC | | | SCAC4 |
| 2806 | OPTN | OIL PATCH TRANSPORTATION INC | | | SCAC4 |
| 2807 | OPTP | OPTIMUM TRANSPORTATION INC | | | SCAC4 |
| 2808 | OPTQ | ON POINT TRANSPORTATION INC | | | SCAC4 |
| 2809 | OPTS | O & P TRUCK SERVICE | | | SCAC3 |
| 2810 | OPTT | OPTIMUM LOGISTICS INC | | | SCAC4 |
| 2811 | OPTU | OPTIMODAL INC | | USA | BIC |
| 2812 | OPTU | Optimodal | | | RSRV |
| 2813 | OPTU | OPTIMODAL INC | | | SCAC4 |
| 2814 | OPUC | Oshawa Public Utilities Commission | | CDN | TRAFFIC |
| 2815 | OPUD | ONG PICK-UP & DELIVERY SERVICE | | | SCAC4 |
| 2816 | OPUS | OPUS-ONE CARGO CORP | | | SCAC4 |
| 2817 | OPV | Bedarfsflugunternehmen Dr. L. Polsterer | IATA: OE, Callsign: Polsterer, | A | AVCODES |
| 2818 | OPV | Operadora de Veulos Ejectutivos | | | ICAO1 |
| 2819 | OPVI | OLD PUEBLO VAN & STORAGE INC | | | SCAC3 |
| 2820 | OPWI | OVERFLO PUBLIC WAREHOUSE INC | | | SCAC3 |
| 2821 | OPWI | OVERFLO WAREHOUSE INC | | | SCAC4 |
| 2822 | OPX | Ohio Power Co. | added 10/1958; 4/1961-7/2005 | | NAKINA |
| 2823 | OPX | The Ohio Power Co. | 1/1943-10/1957; eliminated 10/1958 | | NAKINA |
| 2824 | OPX | The Ohio Power Co. | 1/52-10/57; eliminated 10/58 | | NRHS |
| 2825 | OPX | Ohio Power Co. | added 10/58; 4/61-7/2000 | | NRHS |
| 2826 | OPX | OHIO POWER CO. | | | PWRC |
| 2827 | OPX | Ohio Power | | | RSRV |
| 2828 | OPX | OHIO POWER CO. | | | SCAC4 |
| 2829 | OPXP | OCEAN PACIFIC EXPRESS | | | SCAC4 |
| 2830 | OQ | Express Air, Inc d/b/a Sunrise Airlines | ICAO: FXA, Callsign: Effex, Name changed to Sunrise Airlines Inc | USA | AVCODES |
| 2831 | OQ | Sunrise Airlines, Inc. | ICAO: FXA, Callsign: Effex, Designator OQ* recalled by IATA. Name changed from Express Air, Inc d/b/a Sunrise Airlines | USA | AVCODES |
| 2832 | OQ | Zambian Express Airways (19195) Limited | ICAO: SZX, Callsign: Zambex, Designator OQ recalled by IATA | Z | AVCODES |
| 2833 | OQ | Aeronaves Queen S.A. (Queen Air) | ICAO: QNA, Callsign: Queen Air, | DOM | AVCODES |
| 2834 | OQ | Chong Qing Airlines Co., Ltd | ICAO: CQN, Callsign: Chong Qing, Founded on 16 June 2007. Commenced operations on 08 July 2007. | PRC | AVCODES |
| 2835 | OQ | Scoot Private Ltd | ICAO: SCO, Callsign: Scooter, IATA Prefix: 668, IATA Designator changed to TZ w.e.f. 14 May 2012. | SGP | AVCODES |
| 2836 | OQDD | OSLO LADY LIMITED | | | SCAC3 |
| 2837 | OQFI | ORIENT FREIGHT INTERNATIONAL INC | | | SCAC3 |
| 2838 | OQGL | OFFSHORE LOGISTICS LLC | | | SCAC4 |
| 2839 | OQLL | OQUINN LOGISTICS LLC | | | SCAC4 |
| 2840 | OQNJ | OQUENDO, JOE TRUCKING | | | SCAC3 |
| 2841 | OQNJ | OQUENDO, JOE TRUCKING | | | SCAC4 |
| 2842 | OQNN | OQUINN TRUCK LINES INC | | | SCAC4 |
| 2843 | OQPE | OSLO EMPRESS | | | SCAC3 |
| 2844 | OQPS | OCTOPUS SHIPPING INC. | | | SCAC3 |
| 2845 | OQTI | OPTIMUM QUALITY TRANSFERS INC | | | SCAC4 |
| 2846 | OR | Crimea Air | ICAO: CRF, Callsign: Crimea Air, IATA Prefix: 107, Name changed to KRYM, Limited Partnership International Airline. Designator OR* reinstated by IATA | UA | AVCODES |
| 2847 | OR | Crimea Air | ICAO: CRF, Callsign: Crimea Air, IATA Prefix: 107, Designator OR* recalled by IATA | UA | AVCODES |
| 2848 | OR | Air Comores | Callsign: Aircomor, Designator OR recalled by IATA | COM | AVCODES |
| 2849 | OR | TUI Airlines Nederlands B.V. t/a Arkefly | ICAO: TFL, Callsign: Arkefly, Name changed to TUI Airlines Nederlands B.V. t/a Arke w.e.f. 01 October 2013. ICAO callsign changed to Orange. | NL | AVCODES |
| 2850 | OR | TUI Airlines Nederlands B.V. t/a Arke | ICAO: TFL, Callsign: Orange, Name changed from TUI Airlines Nederlands B.V. t/a Arkefly w.e.f. 01 October 2013. ICAO callsign changed from Arkefly. | NL | AVCODES |
| 2851 | OR | TUI Airlines Nederlands B.V. t/a TUI fly Netherlands | ICAO: TFL, Callsign: Orange, Name changed from TUI Airlines Nederlands B.V. t/a Arke w.e.f. 01 October 2015. ICAO callsign changed from Arkefly. | NL | AVCODES |
| 2852 | OR | Owasco River | 1/1975-1/1980 | | NAKINA |
| 2853 | OR | Owasco River | 1/75-1/80 | | NRHS |
| 2854 | OR | *OAHU RAILWAY, INC. | | | PWRC |
| 2855 | OR | *OWASCO RIVER RAILWAY | | | PWRC |
| 2856 | OR | Owasco River Railway | | | RSRV |
| 2857 | ORA | Montauk Caribbean Airways, Inc. d/b/a Long Island Airlines | Callsign: Long Island, | USA | AVCODES |
| 2858 | ORA | Long Island Airlines | | | ICAO1 |
| 2859 | ORA | Ormet R.R. Corp. | 7/2000-7/2005 | | NAKINA |
| 2860 | ORA | Ormet R.R. Corp. | Jul-00 | | NRHS |
| 2861 | ORA | ORMET RAILROAD CORP. | | | PWRC |
| 2862 | ORA | Ormet Railroad | | | RSRV |
| 2863 | ORAC | ORANGE COUNTY DELIVERY SERVICE INC | | | SCAC4 |
| 2864 | ORAD | ORCON DE MEXICO S A DE C V | | | SCAC4 |
| 2865 | ORAG | ORSAG TRUCKING | | | SCAC4 |
| 2866 | ORAN | ORANGE TERMINAL | | | PWRC |
| 2867 | ORAN | ORANGE EMPIRE TRUCK LINES, INC | | | SCAC3 |
| 2868 | ORAN | ORANGE TKO | | | SCAC4 |
| 2869 | ORAU | INTERMODAL LOGISTICS PLUS LLC | | RUS | BIC |
| 2870 | ORAU | ORIENT AUSTRALIA PTY LTD | | | SCAC4 |
| 2871 | ORB | Orenburg Airlines Federal State Unitary Enterprise | {IATA: R2, Callsign: Orenburg, IATA Prefix: 291, Name changed to JSC "Orenburg Airlines". Name changed from State Unitary Avia Enterprise d/b/a Orenburg Airlines. Designator R2 reinstated by IATA};SRCKEY=AVCODES | RUS | |
| 2872 | ORB | JSC "Orenburg Airlines" | {IATA: R2, Callsign: Orenburg, IATA Prefix: 291, Merged into Rossiya Airlines JSC (FV/SDM) w.e.f. 26 May 2016. Name changed to JSC "Orenburg Airlines". Name changed from State Unitary Avia Enterprise d/b/a Orenburg Airlines. Designator R2 reinstated by IATA};SRCKEY=AVCODES | RUS | |
| 2873 | ORB | State Unitary Avia Enterprise d/b/a Orenburg Airlines | IATA: R2, Callsign: Orenburg, IATA Prefix: 291, Name changed to Orenburg Airlines Federal State Unitary Enterprise | RUS | AVCODES |
| 2874 | ORB | Orenburg Airlines | IATA: R2 | | ICAO1 |
| 2875 | ORB | ORANGE BELT STAGES | | | SCAC4 |
| 2876 | ORBA | ORBITRANS AIR FREIGHT INC | | | SCAC3 |
| 2877 | ORBC | ORBCO | | | SCAC3 |
| 2878 | ORBI | ORBITAL TRANSPORT INC | | | SCAC3 |
| 2879 | ORBIS | Orbis Interntional | Orbis International is an international non-profit non-governmental organization (NGO) dedicated to saving sight worldwide.[ | USA | TRAFFIC |
| 2880 | ORBM | ORMSBY & BAUMEZ JR | | | SCAC3 |
| 2881 | ORBN | ORBIT TRANSPORT & STORAGE INC | | | SCAC3 |
| 2882 | ORBN | ORBIS EXPRESS INC | | | SCAC4 |
| 2883 | ORBO | ORTON, BOB TRUCKING | | | SCAC4 |
| 2884 | ORBQ | ORBIT MOVING & STORAGE INC | | | SCAC3 |
| 2885 | ORBQ | ORBIT MOVING & STORAGE INC | | | SCAC4 |
| 2886 | ORBU | ORBIT CHEMICAL INDUSTRIES LIMITED | | EAK | BIC |
| 2887 | ORBU | ENTERPRISE CONTAINER LINES | | | SCAC3 |
| 2888 | ORBU | ORBIT CHEMICAL INDUSTRIES LTD | | | SCAC4 |
| 2889 | ORBY | ORMSBY TRUCKING INC | | | SCAC3 |
| 2890 | ORBY | ORMSBY TRUCKING INC | | | SCAC4 |
| 2891 | ORC | Air Cordial Limited | Callsign: Cordiale, | GB | AVCODES |
| 2892 | ORC | Oriental Air Bridge Co. Ltd. | IATA: OC, Callsign: Oriental Bridge, IATA designator changed from O3. ICAO Designator changed to NGK. | J | AVCODES |
| 2893 | ORC | OGEECHEE RAILROAD CO. | | | PWRC |
| 2894 | ORC | OGEECHEE RAILROAD COMPANY | | | SCAC4 |
| 2895 | ORC | Oriental Air Bridge | | J | TRAFFIC |
| 2896 | ORCA | ORCAS ISLAND FREIGHT LINES, INC | | | SCAC3 |
| 2897 | ORCA | ORCAS ISLAND FREIGHT LINES INC | | | SCAC4 |
| 2898 | ORCD | ORCHARD TRANSPORT LTD | | | SCAC3 |
| 2899 | ORCD | ORCHARD TRANSPORT LTD | | | SCAC4 |
| 2900 | ORCF | ORCHARD HILL FARMS INC | | | SCAC4 |
