| 2201 | OMNX | Omnisource (Steel Dynamics) | | | RSRV |
| 2202 | OMNX | OMNISOURCE CORPORATION | | | SCAC4 |
| 2203 | OMNX | OmniSource Corp. | | USA | TRAFFIC |
| 2204 | OMOE | OMO ELEWA | | | SCAC4 |
| 2205 | OMOS | OWOBLOW MOTORS | | | SCAC4 |
| 2206 | OMOV | OTHER MOVING COMPANY INC, THE | | | SCAC4 |
| 2207 | OMPM | OMPM TRANS | | | SCAC3 |
| 2208 | OMPS | OMPS H H INC | | | SCAC3 |
| 2209 | OMPS | OMPS H H INC | | | SCAC4 |
| 2210 | OMPT | OMALLEY, P T LUMBER CO INC | | | SCAC4 |
| 2211 | OMPU | OMP ENGINEERING SRL | | I | BIC |
| 2212 | OMR | Minair | Callsign: Ormine, | RCA | AVCODES |
| 2213 | OMR | Minair | | | ICAO1 |
| 2214 | OMRL | OCEANIC MARINE LTD. | | | SCAC3 |
| 2215 | OMRP | OMR PIPELINE COMPANY | | | SCAC3 |
| 2216 | OMRT | OMAR TRUCKING INC | | | SCAC3 |
| 2217 | OMRU | 1MROBOTICS LTD | | IL | BIC |
| 2218 | OMRV | OLE MAN RIVER TOWING INC | | | SCAC3 |
| 2219 | OMRX | Ozark Mountain Railcar LLC | 7/2005 (not listed) | | NAKINA |
| 2220 | OMRX | Mather Stock Car Co. | 1/1941 | | NAKINA |
| 2221 | OMRX | Oscar Mayer & Co. | 7/1937-4/1938 | | NAKINA |
| 2222 | OMRX | Oscar Mayer & Co., Inc. (cars No. 3001-3020, 4001-4020 & 5001-5025) (Union Refrigerator Transit Co.) | 7/1935 | | NAKINA |
| 2223 | OMRX | Oscar Mayer & Co., Inc. (cars No. 2000-2044) (General American Tank Car Corp.) | 7/1935 | | NAKINA |
| 2224 | OMRX | Oscar Mayer & Co., Inc. | 7/1923-7/1932 | | NAKINA |
| 2225 | OMRX | Oscar Meyer & Co. (cars no. 501-599, 801-899) (Mather Stock Car Co.) | Apr-38 | | NRHS |
| 2226 | OMRX | *OSCAR MAYER & CO. (MATHER STOCK CAR CO.) | | | PWRC |
| 2227 | OMRX | +OZARK MOUNTAIN RAILCAR | | | PWRC |
| 2228 | OMRX | Ozark Mountain Railcar | | | RSRV |
| 2229 | OMRX | OZARK MOUNTAIN RAILCAR LLC | | | SCAC4 |
| 2230 | OMS | Omskavia Airline, Public Joint-Stock Society | IATA: N3, Callsign: Omsk, IATA Prefix: 753, | RUS | AVCODES |
| 2231 | OMS | SalamAir | IATA: OV, Callsign: Mazoon, | OM | AVCODES |
| 2232 | OMS | Omskavia Airline | IATA: N3 | | ICAO1 |
| 2233 | OMSC | OLSON, FRED, MOTOR SERVICE COMPANY | | | SCAC3 |
| 2234 | OMSE | OMO-SET | | | SCAC4 |
| 2235 | OMSG | OMNI SHPPING INC | | | SCAC3 |
| 2236 | OMSG | OMNI MARITIME INC | | | SCAC4 |
| 2237 | OMSH | OMEGA SHIPPING (CA) INC | | | SCAC3 |
| 2238 | OMSH | OKOTECH MACHINE SHOP INC | | | SCAC4 |
| 2239 | OMSI | OMAHA MAIL SERVICE | | | SCAC3 |
| 2240 | OMSI | OMNI MOVING AND STORAGE INC | | | SCAC4 |
| 2241 | OMSL | OLYMPIC MOVING & STORAGE II LLC | | | SCAC4 |
| 2242 | OMSN | OTAY MESA SALES INC | | | SCAC4 |
| 2243 | OMSP | OMEGA SHIPPING CO INC | | | SCAC4 |
| 2244 | OMSQ | OVERSEAS MOVING SPECIALISTS INC | | | SCAC4 |
| 2245 | OMSU | ORICA MINING SERVICES PORTUGAL | | P | BIC |
| 2246 | OMSV | OMNI MOVING & STORAGE OF VIRGINIA I | | | SCAC3 |
| 2247 | OMSX | J.T. Leasing Inc. d/b/a Ohio Mulch | 7/2005 (not listed) | | NAKINA |
| 2248 | OMSX | J. T. LEASING CO. d/b/a OHIO MULCH | | | PWRC |
| 2249 | OMSX | Ohio Mulch (J. T. Leasing) | | | RSRV |
| 2250 | OMSX | OHIO MULCH | | | SCAC4 |
| 2251 | OMSY | OMARA MOVING SYSTEMS INC | | | SCAC4 |
| 2252 | OMT | Castillo Mourra | | HN | AVCODES |
| 2253 | OMTA | OMEGA TRANSPORT CORP | | | SCAC3 |
| 2254 | OMTA | OM TRANSPORT INC | | | SCAC4 |
| 2255 | OMTB | OMNI TRANSPORTATION INC | | | SCAC3 |
| 2256 | OMTB | OM TRUCKING | | | SCAC4 |
| 2257 | OMTC | OMNITRON CORPORATION | | | SCAC3 |
| 2258 | OMTD | OMNITRADE SHIPPING COMPANY | | | SCAC3 |
| 2259 | OMTE | ONE MORE TIME RACING STABLES | | | SCAC4 |
| 2260 | OMTG | OMEGA TRUCKING INC | | | SCAC3 |
| 2261 | OMTH | OZARK MTN TRUCKING INC | | | SCAC4 |
| 2262 | OMTI | OSIA MARINE TRADING INC. | | | SCAC3 |
| 2263 | OMTI | OMNI TRANSPORTATION INC | | | SCAC4 |
| 2264 | OMTK | OLGA TRUCKLINE INC | | | SCAC3 |
| 2265 | OMTK | OM TRUCKING | | | SCAC4 |
| 2266 | OMTL | OMNI TRUCK LINE | | | SCAC3 |
| 2267 | OMTN | OMNI TRANSPORTATION SERVICES INC | | | SCAC3 |
| 2268 | OMTN | OMNI TRANSPORTATION SERVICES INC | | | SCAC4 |
| 2269 | OMTP | OMNI TRANSPORTATION COMPANY INC | | | SCAC3 |
| 2270 | OMTQ | OHIO MOTOR TRANSPORTATION CO | | | SCAC3 |
| 2271 | OMTR | OLDE MERIT TRANSPORTATION INC | | | SCAC3 |
| 2272 | OMTR | OMEGA TRANSPORTACIONES | | | SCAC4 |
| 2273 | OMTV | OTTAWA METRO TOWING AND RECOVERY IN | | | SCAC4 |
| 2274 | OMTX | Oscar Mayer & Co. | 1/1941-1/1950 | | NAKINA |
| 2275 | OMUS | Oberleitungbus-Museum Solingen | | D | TRAFFIC |
| 2276 | OMUY | OLMSTEAD, MURRAY | | | SCAC4 |
| 2277 | OMV | OMV PETROM SA | | RO | VKM |
| 2278 | OMVB | OMV Bulgaria OOD | | BG | VKM |
| 2279 | OMVL | OMAR TREVINO, LUIS | | | SCAC4 |
| 2280 | OMVS | OMNI MOVING & STORAGE INC | | | SCAC3 |
| 2281 | OMVS | OLYMPIC MOVING & STORAGE | | | SCAC4 |
| 2282 | OMWD | OMNI WAREHOUSE & DISTRIBUTION INC | | | SCAC3 |
| 2283 | OMWD | OVERSEAS MOTORS WINDSOR INC | | | SCAC4 |
| 2284 | OMWI | OMEGA WAREHOUSING INC | | | SCAC3 |
| 2285 | OMWI | OMEGA WAREHOUSING INC | | | SCAC4 |
| 2286 | OMWN | OVERSEA MOTORS (WINDSOR) INC | | | SCAC4 |
| 2287 | OMWT | OMEGA WORLD TRAVEL | | | SCAC3 |
| 2288 | OMX | National Car Co. | eliminated 1/1963 | | NAKINA |
| 2289 | OMX | Fruit Growers Express Co. | 10/1957-4/1961 | | NAKINA |
| 2290 | OMX | National Car Co. | 1/1950-7/1954 | | NAKINA |
| 2291 | OMX | National Car Co. | Jan-52 | | NRHS |
| 2292 | OMX | Fruit Growers Express Co. | 10/57-4/61 | | NRHS |
| 2293 | OMX | OSCAR MAYER & CO. (NCCO [FRUIT GROWERS EXPRESS]) | | | PWRC |
| 2294 | OMXC | OMARS TRANSPORT LLC | | | SCAC4 |
| 2295 | OMXP | ORLEANS MOTOR EXPRESS, INC | | | SCAC3 |
| 2296 | OMXT | OLLA MESSA TRANSPORT INC | | | SCAC4 |
| 2297 | OMXU | OLAM ENERGY SA DE CV. | | MEX | BIC |
| 2298 | OMZ | OMAK MILL | | | PWRC |
| 2299 | ON | Air Nauru | ICAO: RON, Callsign: Air Nauru, IATA Prefix: 123, Commenceds operation on 14 February 1970. Ceased operations on 18 December 2005. Relaunched as Nauru Air Corporation t/a Our Airline on 14 October 2006. Designator ON reinstated by IATA | NAU | AVCODES |
| 2300 | ON | Nauru Air Corporation t/a Our Airline | ICAO: RON, IATA Prefix: 123, Nauru Air Corporation t/a Nauru Airlines w.e.f. 01 August 2014. Name changed from Air Nauru on 14 October 2005. | NAU | AVCODES |
