| 1201 | OGEE | Ogeechee Railway | | | RSRV |
| 1202 | OGEE | OGEECHEE RAILWAY COMPANY | | | SCAC3 |
| 1203 | OGEG | Österreichische Gesellschaft für Eisenbahngeschichte | | A | TRAFFIC |
| 1204 | OGEG | Österreichische Gesellschaft für Eisenbahngeschichte (ÖGEG) | | AT | VKM |
| 1205 | OGEM | OGEM TRANSPORT INC | | | SCAC4 |
| 1206 | OGEN | OGDEN EXPRESS | | | SCAC3 |
| 1207 | OGEP | OVERSEAS GLOBE EXPRESS | | | SCAC4 |
| 1208 | OGEX | Oklahoma Gas and Electric Co. | added 7/1976; 1/1980-7/2005 | | NAKINA |
| 1209 | OGEX | Oklahoma Gas and Electric Co. | added 7/76; 1/80-7/2000 | | NRHS |
| 1210 | OGEX | OKLAHOMA GAS & ELECTRIC COMPANY | | | PWRC |
| 1211 | OGEX | Oklahoma Gas and Electric | | | RSRV |
| 1212 | OGEX | OKLAHOMA GAS & ELECTRIC | | | SCAC4 |
| 1213 | OGEZ | OGDAN ELEVATOR | | | PWRC |
| 1214 | OGGN | OMEGA CARTAGE INC | | | SCAC3 |
| 1215 | OGHT | OPEN GATE HORSE TRANSPORTATION CO I | | | SCAC3 |
| 1216 | OGI | Aerogisa, S.A. de C.V. | Callsign: Aerogisa, | MEX | AVCODES |
| 1217 | OGI | Aerogisa | | | ICAO1 |
| 1218 | OGIL | OGILBY TRANSFER AND STORAGE COMPANY | | | SCAC3 |
| 1219 | OGIN | O & G INDUSTRIES INC | | | SCAC3 |
| 1220 | OGIP | O & G INDUSTRIES-TUTOR PERINI CORPO | | | SCAC4 |
| 1221 | OGIS | ODIN GEMI ISLETMECILIGI | | | SCAC4 |
| 1222 | OGIT | ORION GROUP INC, THE | | | SCAC4 |
| 1223 | OGIX | O&G INDUSTRIES, INC. | | | PWRC |
| 1224 | OGIX | O & G INDUSTRIES INC | | | SCAC4 |
| 1225 | OGJ | Bakoji Airlines Services Ltd. | Callsign: Bako Air, | WAN | AVCODES |
| 1226 | OGJ | Bakoji Airlines Services | | | ICAO1 |
| 1227 | OGKG | OSEGUERA TRUCKING | | | SCAC4 |
| 1228 | OGLB | OGLEBAY NORTON COMPANY | | | SCAC3 |
| 1229 | OGLL | ONE GLOBAL LOGISTICS LLC | | | SCAC4 |
| 1230 | OGLN | OTS GLOBAL LOGISTICS INC | | | SCAC4 |
| 1231 | OGLQ | OLIGSCHLAEGER, EMIL | | | SCAC3 |
| 1232 | OGLT | OGLE TRUCKING | | | SCAC3 |
| 1233 | OGLT | OLSENS GRAIN & LIVESTOCK | | | SCAC4 |
| 1234 | OGMS | O BRIENS-GLOSE MOVING & STORAGE | | | SCAC3 |
| 1235 | OGMT | ORGANIC MATTERS | | | SCAC4 |
| 1236 | OGN | Origin Pacific Airways Limited | IATA: QO, Callsign: Origin, Founded in 1996. Commenced operatins in April 1997. Ceased passenger operations on 10 August 2006 and cargo operation on 15 September 2006. Placed into Receivership on 15 September 2006. | NZ | AVCODES |
| 1237 | OGN | Origin Pacific Airways | IATA: QO | | ICAO1 |
| 1238 | OGOL | OGO MARKETING LLC | | | SCAC4 |
| 1239 | OGOM | ORTEZ GUERRERO, OMAR | | | SCAC4 |
| 1240 | OGOX | Oklahoma Gasoline & Oil Co. | 7/1923 | | NAKINA |
| 1241 | OGOX | OKLAHOMA GASOLINE & OIL CO. | | | PWRC |
| 1242 | OGPT | ORION GROUP, THE | | | SCAC4 |
| 1243 | OGPU | ROZA MIRA LLC | | RUS | BIC |
| 1244 | OGPX | Oklahoma Gasoline Plants, Inc. | 7/1930-1/1943 | | NAKINA |
| 1245 | OGPX | Oklahoma Gasoline Plants, Inc. | Apr-38 | | NRHS |
| 1246 | OGPX | OKLAHOMA GASOLINE PLANTS, INC. | | | PWRC |
| 1247 | OGRE | OGRADY, ED | | | SCAC3 |
| 1248 | OGRE | ORGANIC GREENS | | | SCAC4 |
| 1249 | OGRP | OTT GROUP | | | SCAC4 |
| 1250 | OGRT | OGRADY TRUCKING | | | SCAC3 |
| 1251 | OGSD | OFERTAS GUAJARDO SA DE CV | | | SCAC4 |
| 1252 | OGSI | OCEAN GOLD SEAFOODS INC | | | SCAC4 |
| 1253 | OGSP | OLD GLASS SHOP, THE | | | SCAC4 |
| 1254 | OGSX | Alliant Energy | added 4/2000; 7/2000; eliminated 1/2002; 7/2005 | | NAKINA |
| 1255 | OGSX | IES Utilities, Inc. | added 1/1996; eliminated 4/2000 | | NAKINA |
| 1256 | OGSX | Iowa Southern Utilities Co. | added 7/1980; 1/1994; eliminated 1/1996 | | NAKINA |
| 1257 | OGSX | Iowa Southern Utilities Co. | added 7/80; 1/94; eliminated 1/96 | | NRHS |
| 1258 | OGSX | IES Utilities, Inc. | added 1/96; eliminated 4/2000 | | NRHS |
| 1259 | OGSX | Alliant Energy | added 4/2000; 7/2000 | | NRHS |
| 1260 | OGSX | ALLIANT ENERGY {IES UTILITIES INCORPORATED; IOWA SOUTHERN UTILITIES CO.] | | | PWRC |
| 1261 | OGSX | Iowa Southern Utilities | | | RSRV |
| 1262 | OGSX | ALLIANT ENERGY | | | SCAC4 |
| 1263 | OGSY | OLYMPIAN GROUP SYSTEMS INC | | | SCAC4 |
| 1264 | OGTN | ONE GOOD TURN | | | SCAC4 |
| 1265 | OGTS | ORGANIZADORA DE TRANSPORTES SA DE C | | | SCAC4 |
| 1266 | OGTU | ORPHAN GRAIN TRAIN INC. | | USA | BIC |
| 1267 | OGTU | Orphan Grain Train | | | RSRV |
| 1268 | OGVL | OLD GLORY VAN LINES LLC | | | SCAC4 |
| 1269 | OGWS | OURS GARAGE & WRECKER SERVICE INC | | | SCAC4 |
| 1270 | OGXL | OLINGER TRANSPORT LLC | | | SCAC4 |
| 1271 | OGXN | OMEGA EXPRESS INC | | | SCAC3 |
| 1272 | OGXN | ORIGINAL EXHAUST MANUFACTURERS INC | | | SCAC4 |
| 1273 | OGZK | OGORZOLKA TRANSPORTATION INC | | | SCAC4 |
| 1274 | OH | PSA Airlines | ICAO: JIA, Callsign: Blue Streak, Name reverted to Jetstream International Airlines. Changed name from Jetstream International Airlines w.e.f. 01 November 1995. US Airways Express Carrier | USA | AVCODES |
| 1275 | OH | Comair, Inc. | ICAO: COM, Callsign: Comair, IATA Prefix: 886, Ceased operations on 29 September 2012 | USA | AVCODES |
| 1276 | OH | SFO Helicopter Airlines, Inc. | Callsign: SFO Airlines, | USA | AVCODES |
| 1277 | OH | XP International BV | ICAO: XPS, Callsign: XP Parcel, Ceased operations. Designator OH recalled by IATA | NL | AVCODES |
| 1278 | OH | Jetstream International Airlines | ICAO: JIA, Callsign: Blue Streak, Name from PSA Airlines. Changed name from Jetstream International Airlines w.e.f. 01 November 1995. US Airways Express Carrier | USA | AVCODES |
| 1279 | OHA | Air Odon | Callsign: Air Odon, | F | AVCODES |
| 1280 | OHA | O.H. Aviation | | F | AVCODES |
| 1281 | OHAD | OHIO AUTO DELIVERY | | | SCAC3 |
| 1282 | OHAD | ORMAN BROTHERS | | | SCAC4 |
| 1283 | OHAF | O H & F INC | | | SCAC3 |
| 1284 | OHAJ | OHARA, J F & SON INC | | | SCAC3 |
| 1285 | OHAR | OHARA CORPORATION | | | SCAC4 |
| 1286 | OHAT | OCHOA'S TRUCKING | | | SCAC4 |
| 1287 | OHAV | O'HARE VAN LINES, INC | | | SCAC3 |
| 1288 | OHBL | OHIO BARGE LINE INC, | | | SCAC3 |
| 1289 | OHBL | OHIO BARGE LINE INC, | | | SCAC4 |
| 1290 | OHC | Jet Select, LLC | Callsign: Ohio-Charter, Merged into Jet Edge. | USA | AVCODES |
| 1291 | OHCC | OHIO CARRIER CORPORATION | | | SCAC3 |
| 1292 | OHCD | O'HARE COLD CO | | | SCAC4 |
| 1293 | OHCN | OHIO CONNECTION | | | SCAC3 |
| 1294 | OHCN | OHC INTERMODAL | | | SCAC4 |
| 1295 | OHCR | Ohio Central R.R. Inc. | 1/1994-7/2005 | | NAKINA |
| 1296 | OHCR | The Columbus & Ohio River R.R. Co. | added 10/1992 | | NAKINA |
| 1297 | OHCR | Ohio R.R. System | eliminated 10/1992 | | NAKINA |
| 1298 | OHCR | Ohio Central R.R. Inc. | added 7/1988; 1/1994 | | NAKINA |
| 1299 | OHCR | Ohio Central R.R. Inc. | added 7/88; 1/94 | | NRHS |
| 1300 | OHCR | Ohio R.R. System | eliminated 10/92 | | NRHS |
