| 3101 | ORR | OSAGE RAILROAD | | | PWRC |
| 3102 | ORR | Osage Railroad | | | RSRV |
| 3103 | ORRC | ORRICK TRANSPORTATION | | | SCAC3 |
| 3104 | ORRC | OSMOSE RAIL ROAD SERVICES INC | | | SCAC4 |
| 3105 | ORRG | OCEAN RAIL ROAD LOGISTICS INC | | | SCAC4 |
| 3106 | ORRI | OMNI RESOURCE RECOVERY INC | | | SCAC4 |
| 3107 | ORRK | ORROCK & SONS TRUCKING INC | | | SCAC4 |
| 3108 | ORRQ | ORR TANK LINES | | | SCAC3 |
| 3109 | ORRR | ORR, ROBERT B INC | | | SCAC3 |
| 3110 | ORRS | ORRIS TRUCKING INC | | | SCAC3 |
| 3111 | ORRS | ORR, SAMMY TRUCKING CO | | | SCAC4 |
| 3112 | ORRV | ORR, VINCE TRUCKING INC | | | SCAC3 |
| 3113 | ORRW | ORRWAY MOTOR SERVICE INC | | | SCAC3 |
| 3114 | ORRX | Oregon Dept. of Transportation/Rail Division | added 10/2003; 7/2005; eliminated 1/2007 | | NAKINA |
| 3115 | ORRX | OREGON DEPT. OF TRANSPORTATION RAIL DIVISION | | | PWRC |
| 3116 | ORS | Action Air S.r.l. | Callsign: Aviation Service, | I | AVCODES |
| 3117 | ORS | Action Air | | | ICAO1 |
| 3118 | ORSA | ORSA-MAGGIORE TRANSPORTATION | | | SCAC4 |
| 3119 | ORSA | Orsatåg AB | 1998 - 2003 | S | TRAFFIC |
| 3120 | Orsatåg | Orsatåg AB | 1998 - 2003 | S | svenska-lok.se |
| 3121 | ORSC | ORSCHELN CO | | | SCAC3 |
| 3122 | ORSE | O'ROURKE SALES | | | SCAC4 |
| 3123 | ORSG | ON THE ROAD SALES AGENTS | | | SCAC4 |
| 3124 | ORSH | ONLINE ROPE STORE, THE | | | SCAC4 |
| 3125 | ORSI | OROSI TRUCKING INC | | | SCAC3 |
| 3126 | ORSI | ORANGE RECYCLING SERVICES INC | | | SCAC4 |
| 3127 | ÖrSJ | Örebro - Svartå | 1897 - 1907 | S | svenska-lok.se |
| 3128 | ORSL | ORINOGO SHIPPING CO LTD | | | SCAC3 |
| 3129 | ORSL | ORINOCO SHIPPING CO LTD | | | SCAC4 |
| 3130 | ORSR | ORIENT SHIPPING ROTTERDAM | | | SCAC4 |
| 3131 | ORSX | Oxweld Railroad Service Co. | 1/1941-4/1961 (not listed) | | NAKINA |
| 3132 | ORSX | Oxweld Railroad Service Co. | 1/52-4/61 | | NRHS |
| 3133 | ORSX | OXWELD RAILROAD SERVICE CO. | | | PWRC |
| 3134 | ORT | Air Orient | IATA: UT, Callsign: Air Orient, Desigantor UT recalled by IATA. Name changed from Air Charter Asia | F | AVCODES |
| 3135 | ORT | Air Charter Asia | IATA: UT, Name changed to Air Orient | F | AVCODES |
| 3136 | ORT | Ortac AOC Ltd. | Callsign: Skywalker, | GBJ | AVCODES |
| 3137 | ORTA | ORTIZ INTERNATIONAL INC | | | SCAC4 |
| 3138 | ORTB | ORTIZ BROTHERS MOVING & STORAGE | | | SCAC4 |
| 3139 | ORTC | OLSEN, ROE TRANSFER COMPANY | | | SCAC3 |
| 3140 | ORTC | ORT, TOM TRUCKING INC | | | SCAC4 |
| 3141 | ORTE | OREGON TRAILER CONVOY | | | SCAC3 |
| 3142 | ORTF | ORANGE TRANSFER COMPANY | | | SCAC3 |
| 3143 | ORTG | ORT, GERALD E TRUCKING INC | | | SCAC3 |
| 3144 | ORTG | OPEN RANGE TRUCKING | | | SCAC4 |
| 3145 | ORTI | ORIENTAL TILE IMPORTERS INC | | | SCAC3 |
| 3146 | ORTI | OAK RUN TRANSPORTATION INC | | | SCAC4 |
| 3147 | ORTJ | O & R TRUCKING | | | SCAC4 |
| 3148 | ORTK | O & R TRUCKING | | | SCAC4 |
| 3149 | ORTL | ORTLIEB MOVING & STORAGE CO | | | SCAC3 |
| 3150 | ORTL | ORTLIEB MOVING & STORAGE CO | | | SCAC4 |
| 3151 | ORTM | O'NEIL, RYAN TRUCKING LIMITED | | | SCAC4 |
| 3152 | ORTN | OHIO RIVER TRUCKING COMPANY, THE | | | SCAC3 |
| 3153 | ORTN | OROZCO TRANSPORTATION INC | | | SCAC4 |
| 3154 | ORTO | ORTOLANOS EXPRESS | | | SCAC3 |
| 3155 | ORTO | OSCAR TRANSPORTATION | | | SCAC4 |
| 3156 | ORTP | ORBIT TRANSPORT INC | | | SCAC3 |
| 3157 | ORTP | OREGON TRAIL TRANSPORTATION | | | SCAC4 |
| 3158 | ORTQ | ORTNER AIR SERVICE | | | SCAC3 |
| 3159 | ORTS | ORSETTI TRUCK SERVICE | | | SCAC3 |
| 3160 | ORTT | ORTEGA TRUCKING | | | SCAC3 |
| 3161 | ORTU | {ООО "АTLANT"};ZIPCODE=191015 | | RUS | BIC |
| 3162 | ORTV | OREGON TRAIL TRAVEL SERVICE | | | SCAC3 |
| 3163 | ORTV | ORTS TRUCKING LLC | | | SCAC4 |
| 3164 | ORTW | OSWEGO RIVER TOWING LINE INC. | | | SCAC3 |
| 3165 | ORTX | O & R Transport, Inc. | 7/2005 (not listed) | | NAKINA |
| 3166 | ORTX | *OHIO RIVER TERMINAL | | | PWRC |
| 3167 | ORTX | +O & R TRANSPORT, INC. | | | PWRC |
| 3168 | ORTX | O & R TRANSPORT INC | | | SCAC4 |
| 3169 | ORTZ | OREGON TRUNK | | | PWRC |
| 3170 | ORUG | ON TIME SERVICOS TERRESTRES URGENTE | | | SCAC4 |
| 3171 | ORUS | ON ROAD USA EXPRESS | | | SCAC3 |
| 3172 | ORUZ | ORLANDO UTILITIES COMMISSION | | | PWRC |
| 3173 | ORVA | ORVAL KENT DE LINARES SA DE CV | | | SCAC4 |
| 3174 | ORVC | OIL RECOVERY CORPORATION | | | SCAC3 |
| 3175 | ORVC | ORRVILLE CARRIER SERVICE INC | | | SCAC4 |
| 3176 | ORVM | ORANGEVILLE MANUFACTURING CO INC | | | SCAC3 |
| 3177 | ORW | Orwex | | PL | AVCODES |
| 3178 | ORWG | OAK RIDGE WOODWORKING | | | SCAC4 |
| 3179 | ORWT | OVERTON, ROY W TRUCKING CO | | | SCAC4 |
| 3180 | ORWU | On Rail -Gesellschaft für Vermietung | | DE | VKM |
| 3181 | ORX | Oryx Aviation | | ZA | AVCODES |
| 3182 | ORX | Orbit Express Airlines Hava Yollair A.s. (Orex) | IATA: XW, Callsign: Orex, Ceased operations | TR | AVCODES |
| 3183 | ORX | Orbit Express Airlines | | | ICAO1 |
| 3184 | ORXE | ORSCHELN EXPRESS CORPORATION | | | SCAC3 |
| 3185 | ORXE | ORSCHELN, GREG TRANSPORTATION CO | | | SCAC4 |
| 3186 | ORXI | OMAHA REFRIGERATED EXPRESS INC | | | SCAC3 |
| 3187 | ORXM | ORIX MARITIME CORPORATION | | | SCAC3 |
| 3188 | ORXP | ORION EXPRESS LINE | | | SCAC3 |
| 3189 | ORXQ | ORIENT EXPRESS FOOD SUPPLY CO | | | SCAC3 |
| 3190 | ORXT | ORIENT EXPRESS TRANSPORT | | | SCAC4 |
| 3191 | ORXX | NORDEN VIDEO INC | | | SCAC4 |
| 3192 | ORY | OHIO RAILWAY MUSEUM | | | PWRC |
| 3193 | ORYS | ONSTATE RECYCLING INC | | | SCAC3 |
| 3194 | ORZ | Zorex, S.A. | Callsign: Zorex, | E | AVCODES |
| 3195 | ORZ | Zorex | | | ICAO1 |
| 3196 | ORZQ | ORZAK CARTAGE CO | | | SCAC3 |
| 3197 | ORZT | ORTIZ TRUCKING | | | SCAC3 |
| 3198 | OS | Austrian Airlines | ICAO: AUA, Callsign: Austrian, IATA Prefix: 257, Name changed to Austrian Airlines, Osterreichische Luftverkehrs AG d/b/a/ Austrian | A | AVCODES |
| 3199 | 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 |
| 3200 | 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 |
