| 1 | OS | Austrian Airlines | ICAO: AUA, Callsign: Austrian, IATA Prefix: 257, Name changed to Austrian Airlines, Osterreichische Luftverkehrs AG d/b/a/ Austrian | A | AVCODES |
| 2 | OS | Austrian Airlines, Osterreichische Luftverkehrs AG d/b/a/ Austrian | ICAO: AUA, Callsign: Austrian, IATA Prefix: 257, Name changed to Austrian Airlines AG d/b/a/ Austrian. Name changed from Austrian Airlines | A | AVCODES |
| 3 | OS | Austrian Airlines AG d/b/a/ Austrian | ICAO: AUA, Callsign: Austrian, IATA Prefix: 257, Name changed from Austrian Airlines, Osterreichische Luftverkehrs AG d/b/a/ Austrian | A | AVCODES |
| 4 | OS | Ontario Southland Ry. Inc. | 7/2005 | | NAKINA |
| 5 | OS | ONTARIO SOUTHLAND RWY., INC. | | | PWRC |
| 6 | OS | ONTARIO SOUTHLAND RAILWAY INC | | | SCAC4 |
| 7 | OSA | Aero Astra | Callsign: Rostra, | MEX | AVCODES |
| 8 | OSA | Open Sky Aviation | | | ICAO1 |
| 9 | OSAA | OSARPA | | | SCAC4 |
| 10 | OSAAT | Osaka Airport Transortation | Subsidiary of Hankyu Corp. In 2022 merged into Hankyu Kanko Bus | J | TRAFFIC |
| 11 | OSAC | OMEGA SOLUTIONS TRANSPORT INC | | | SCAC4 |
| 12 | OSACB | Osaka City Bus Corporation | Owned by the Osaka Metro Company | J | TRAFFIC |
| 13 | OSAG | OSAGE OIL & TRANSPORTATION INC | | | SCAC3 |
| 14 | OSAG | OSPECA LOGISTICS MANAGEMENT TRANSPO | | | SCAC4 |
| 15 | OSAG | Osterwalder St. Gallen AG | | CH | TRAFFIC |
| 16 | OSAG | Osterwalder St. Gallen AG | | CH | VKM |
| 17 | OSAI | ORINOCO SHIPPING AGENCIES INC | | | SCAC3 |
| 18 | OSAKAB | Osaka Bus Co. | | J | TRAFFIC |
| 19 | OSAM | Osaka Monorail | | J | TRAFFIC |
| 20 | OSAP | OCEANA SHIPPING AG | | | SCAC4 |
| 21 | OSAR | OSAR TRUCKING CO, INC | | | SCAC3 |
| 22 | OSAW | OAKLEY SUB ASSEMBLY WINDSOR | | | SCAC4 |
| 23 | OSB | Osob Airlines | Callsign: Osob, | SO | AVCODES |
| 24 | OSB | Ortenau S-Bahn GmbH | Offenburg (SWEG-Tochter) | D | privat-bahn.de |
| 25 | OSB | Ortenau-S-Bahn | | D | TRAFFIC |
| 26 | OSB | Ortenau-S-Bahn | | DE | VKM |
| 27 | OSBA | OSBORNE TRUCKING CO INC | | | SCAC4 |
| 28 | OSBC | OSBORNES TRUCKING INC | | | SCAC3 |
| 29 | OSBC | OCEANEXPRESS | | | SCAC4 |
| 30 | OSBD | OSBURN, DALE INC | | | SCAC3 |
| 31 | OSBD | OSBORNE PROPELLERS LTD | | | SCAC4 |
| 32 | OSBE | OSBORNES TRUCKING INC | | | SCAC4 |
| 33 | OSBI | OSTERBUR TRUCKING INC | | | SCAC3 |
| 34 | OSBJ | OSBORNE, J R INC | | | SCAC3 |
| 35 | OSBN | OSBORN CARIERS INC | | | SCAC3 |
| 36 | OSBN | OVERSEAS BOSTON LLC | | | SCAC4 |
| 37 | OSBO | OSBORN TRUCKING INC | | | SCAC3 |
| 38 | OSBO | OSBORNE LOGISTICS LLC | | | SCAC4 |
| 39 | OSBP | OFF-SET BASS DRUM PEDAL | | | SCAC4 |
| 40 | OSBS | OSBORN & SON TRUCKING CO, INC | | | SCAC3 |
| 41 | OSBS | Osborn & Son Trucking Co Inc. | | USA | TRAFFIC |
| 42 | OSBT | OSBORNE TRUCKING CO INC | | | SCAC3 |
| 43 | OSBV | OVET SHIPPING BV | | | SCAC4 |
| 44 | OSC | OneSky Aviation Services S.p.a. (OneSky Chile) | Callsign: Uncielo, | RCH | AVCODES |
| 45 | OSC | Osaka Municipal Transportation Bureau | | J | TRAFFIC |
| 46 | OSCA | ONE STOP CRITICAL | | | SCAC4 |
| 47 | OSCC | OMNI/SOUTHEASTERN CHEMICAL CO INC | | | SCAC3 |
| 48 | OSCD | OCEAN STATE COURIER AND DELIVERY IN | | | SCAC3 |
| 49 | OSCD | ONE SEVEN TWO ZERO SIX TWO (172062) | | | SCAC4 |
| 50 | OSCH | OSTLUND CHEMICAL CO | | | SCAC3 |
| 51 | OSCH | OSCAR SHIPMANAGEME | | | SCAC4 |
| 52 | OSCH | | City: Oschersleben | D | TRAFFIC |
| 53 | OSCI | OSULLIVAN CARTAGE INC | | | SCAC3 |
| 54 | OSCK | OXYGEN SERVICE COMPANY INC | | | SCAC4 |
| 55 | OSCL | CONTSHIP OCEEAN STAR SERV. | | | SCAC3 |
| 56 | OSCL | OVERSEAS LNG S2 CORPORATION | | | SCAC4 |
| 57 | OSCM | ORION SHIPMANAGEMENT CO | | | SCAC4 |
| 58 | OSCN | OCEAN STAR CONTAINER LINE | | | SCAC3 |
| 59 | OSCN | OCEAN STAR CONTAINER LINES | | | SCAC4 |
| 60 | OSCO | OSCO SHIPPING A/S | | | SCAC3 |
| 61 | OSCO | ORTHOS SHIPPING CORPORATION | | | SCAC4 |
| 62 | OSCP | OMEGA SHIPPING CO INC | | | SCAC4 |
| 63 | OSCQ | OM SEAFOOD CO INC | | | SCAC4 |
| 64 | OSCT | OLSON, STEVEN C TRUCKING | | | SCAC4 |
| 65 | OSCU | OCI COMPANY LTD | | ROK | BIC |
| 66 | OSCX | Oil Seeds Co. | 8/1920-7/1923 | | NAKINA |
| 67 | OSCX | OIL SEEDS CO. | | | PWRC |
| 68 | OSCZ | INTERMODAL SERVICES, INC. | | | PWRC |
| 69 | OSCZ | Intermodal Services Inc. | | | RSRV |
| 70 | OSCZ | INTERMODAL SERVICES, INC. | | | SCAC4 |
| 71 | OSD | National Airborne Operations Center, U.S. Strategic Command | Callsign: Secdef, | USA | AVCODES |
| 72 | OSDL | OVERSEAS DRILLING LIMITED | | | SCAC4 |
| 73 | OSDT | OSTROM, DARREL TRUCKING LTD | | | SCAC4 |
| 74 | OSDV | OMAXZ SA DE CV | | | SCAC4 |
| 75 | OSE | Ostsächsische Eisenbahnfreunde e.V. | Löbau / Bautzen | D | privat-bahn.de |
| 76 | OSE | | | GR | TRAFFIC |
| 77 | OSE | Organismos Sidirodromon Ellados | | EL | VKM |
| 78 | OSEC | OAKES & SONS ENTERPRIZE CO LLC | | | SCAC4 |
| 79 | OSEE | ONE SIX EIGHT THREE ONE FOUR | | | SCAC4 |
| 80 | OSEE | Ostseebus | | D | TRAFFIC |
| 81 | OSEF | ONE SIX EIGHT SEVEN FIVE ONE | | | SCAC4 |
| 82 | OSEF | Ostsächsische Eisenbahnfreunde e.V | | DE | VKM |
| 83 | OSEK | Austrovapor Bahnnostalgie Veranstaltungs GmbH | | AT | VKM |
| 84 | OSEP | OCEAN STATE EXPRESS INC | | | SCAC3 |
| 85 | OSER | OSER LEASING COMPANY INC | | | SCAC3 |
| 86 | OSER | OBSCURA SANCHEZ, EDUARDO ERIC | | | SCAC4 |
| 87 | OSES | OHIO SOUTHERN EXPRESS INC | | | SCAC3 |
| 88 | OSEY | OSPREY EQUIPMENT CORPORATION | | | SCAC4 |
| 89 | OSFA | OLD SOUTH FREIGHT SERVICES INC | | | SCAC4 |
| 90 | OSFB | ON THE SPOT FREIGHT | | | SCAC4 |
| 91 | OSFC | OLSEN, FRED & CO. | | | SCAC3 |
| 92 | OSFD | OHIO STATE FORWARDING INC | | | SCAC3 |
| 93 | OSFI | OSCEOLA FOOD INC | | | SCAC3 |
| 94 | OSFN | ONE SEVEN FIVE ZERO NINE SEVEN EIGH | | | SCAC4 |
| 95 | OSFS | ON-SITE FUEL SERVICE INC | | | SCAC4 |
| 96 | OSFW | ONE SIX FIVE ONE TWO SIX TWO (16512 | | | SCAC4 |
| 97 | OSGA | OSG DELAWARE BAY LIGHTERING LLC | | | SCAC4 |
| 98 | OSGB | OVERSEAS GALENA BAY LLC | | | SCAC4 |
| 99 | OSGC | OSG CAR CARRIERS, INC. | | | SCAC3 |
| 100 | OSGD | OSTERGARD TRUCKING | | | SCAC4 |
