| 1701 | OKTE | OLD K TRANSPORTATION INC | | | SCAC4 |
| 1702 | OKTF | OK TRANSFER LLC | | | SCAC4 |
| 1703 | OKTG | O K TRUCKING INC | | | SCAC4 |
| 1704 | OKTH | OAKHURST TRANSPORTATION INC | | | SCAC3 |
| 1705 | OKTI | O K TRANSFER & STORAGE CO INC | | | SCAC3 |
| 1706 | OKTK | O K TRUCKING CO INC | | | SCAC3 |
| 1707 | OKTL | OKLAHOMA TANK LINES | | | SCAC3 |
| 1708 | OKTN | O K TRANSPORTATION INC | | | SCAC4 |
| 1709 | OKTO | O K TRANSFER COMPANY | | | SCAC3 |
| 1710 | OKTO | Outokumpu Stainless Oy | | FI | VKM |
| 1711 | OKTQ | OK TRANSFER CO | | | SCAC3 |
| 1712 | OKTQ | OKT INC | | | SCAC4 |
| 1713 | OKTR | O K TRUCKING CO | | | SCAC3 |
| 1714 | OKTT | OK TOURS | | | SCAC4 |
| 1715 | OKTV | OK TO SHIP INC | | | SCAC4 |
| 1716 | OKW | Ok-Trans LLC | | RUS | AVCODES |
| 1717 | OKWBG | ÖKOMBI GmbH | | AT | VKM |
| 1718 | OKWD | OAKWOOD MFG | | | SCAC4 |
| 1719 | OKWH | O K WAREHOUSE CO, INC | | | SCAC3 |
| 1720 | OKWL | OKLAHOMA WESTERN LINES INC | | | SCAC3 |
| 1721 | OKWM | OKEITH, WILLIAM | | | SCAC3 |
| 1722 | OKWS | O K WRECKER SERVICE | | | SCAC3 |
| 1723 | OKWT | OAKWOOD TRANSPORT | | | SCAC4 |
| 1724 | OKWU | NDUNESE SEALAND SDN BHD | | MAL | BIC |
| 1725 | OKXI | OK EXPRESS INC | | | SCAC3 |
| 1726 | OKXL | OKX LOGISTICS INC | | | SCAC4 |
| 1727 | OKXN | OKEANA TRANSPORT | | | SCAC4 |
| 1728 | OKXP | OK EXPRESS | | | SCAC4 |
| 1729 | OKXT | OKLATEX TRANSPORT INC | | | SCAC4 |
| 1730 | OKYT | OAKLEY TRUCKING LLC | | | SCAC4 |
| 1731 | OL | OLT-Ostfriesische Lufttransport | ICAO: OLT, Callsign: Oltra, IATA Prefix: 704, Name changed to OLT Express Germany GmbH. | D | AVCODES |
| 1732 | OL | Odyssey International | ICAO: ODY, Callsign: Odyssey, Founded in June 1988. Ceased operations during April 1990. | CDN | AVCODES |
| 1733 | OL | OLT Express Germany GmbH | ICAO: OLT, Callsign: Oltra, IATA Prefix: 704, Ceased operations on 27 January 2013 at 12:00pm. Name changed from OLT-Ostfriesische Lufttransport. | D | AVCODES |
| 1734 | OL | Polynesian Limited | ICAO: PAO, Callsign: Polynesian, IATA Prefix: 162, Name changed to Samoa Airways in 2017. | WS | AVCODES |
| 1735 | OL | Samoa Airways | ICAO: PAO, Callsign: Polynesian, IATA Prefix: 162, Name changed from Polynesian Limited in 2017. | WS | AVCODES |
| 1736 | OL&I | Ogden, Logan & Idaho Ry. Co. (Utah Idaho Central R.R. Co.) | 7/1930 | | NAKINA |
| 1737 | OL&I | UTAH IDAHO CENTRAL RAILROAD CO. [OGDEN, LOGAN & IDAHO RWY. CO.] | | | PWRC |
| 1738 | OLA | Overland Airways Limited | IATA: OJ, Callsign: Overland, Commenced operations on 26 November 2003. | WAN | AVCODES |
| 1739 | OLA | Overland Airways Limited | IATA: OF, Callsign: Overland, Commenced operations on 26 November 2003. IATA designator changed from OJ. | WAN | AVCODES |
| 1740 | OLA | Overland Airways | IATA: OJ | | ICAO1 |
| 1741 | OLA | Ostseeland Verkehr GmbH | Schwerin (Connex-Gruppe > Veolia Verkehr) | D | privat-bahn.de |
| 1742 | OLA | Ostseeland Verkehr GmbH | | DE | VKM |
| 1743 | OLAE | OLSEN, ARDEN E | | | SCAC3 |
| 1744 | OLAF | OLD SALT FISHING CO LTD | | | SCAC4 |
| 1745 | OLAG | OLAUGHLIN, LEO INC | | | SCAC3 |
| 1746 | OLAO | OLD ALLEN AUTO SALES | | | SCAC3 |
| 1747 | OLAP | OKANOGAN LABEL AND PRINT | | | SCAC4 |
| 1748 | OLAT | OLATHE TRUCKING LLC | | | SCAC4 |
| 1749 | OLAU | OCCIDENTAL CHEMICAL CORPORATION | | | PWRC |
| 1750 | OLAU | Occidental Chemical Corporation | | | RSRV |
| 1751 | OLAU | OCCIDENTAL CHEMICAL CORPORATION | | | SCAC3 |
| 1752 | OLB | Omaha, Lincoln and Beatrice Ry. Co. | added 10/1974; 1/1975-7/2005 | | NAKINA |
| 1753 | OLB | Omaha, Lincoln and Beatrice Ry. Co. | added 10/74; 1/75-7/2000 | | NRHS |
| 1754 | OLB | OMAHA, LINCOLN & BEATRICE RAILWAY COMPANY | | | PWRC |
| 1755 | OLB | Omaha, Lincoln and Beatrice Railway | | | RSRV |
| 1756 | OLBC | OLIVER BUS CO (DIV OF R & R TRUCKIN | | | SCAC3 |
| 1757 | OLBC | OLIN, LARRY M | | | SCAC4 |
| 1758 | OLBE | OLD BRIDGE EXPRESS | | | SCAC3 |
| 1759 | OLBH | OLSEN BROTHERS INC | | | SCAC3 |
| 1760 | OLBI | OCEAN LINE OF BERMUDA INC. | | | SCAC3 |
| 1761 | OLBK | OLSON BROS TRUCKING | | | SCAC3 |
| 1762 | OLBO | OLSEN, W TRANSFER | | | SCAC3 |
| 1763 | OLBZ | OLD BEN #25 MINE | | | PWRC |
| 1764 | OLC | Solar Cargo, C.A. | IATA: 4S, Callsign: Solarcargo, IATA Prefix: 644, | YV | AVCODES |
| 1765 | OLC | Solar Cargo | | | ICAO1 |
| 1766 | OLCC | OLYMPIC CASCADE CORPORATION | | | SCAC3 |
| 1767 | OLCI | OLSON CARRIERS INC | | | SCAC3 |
| 1768 | OLCI | OVERLAND CUSTOM COACH (2007) INC | | | SCAC4 |
| 1769 | OLCL | OLETA COACH LINES INC | | | SCAC3 |
| 1770 | OLCL | OLSEN, L C L INC | | | SCAC4 |
| 1771 | OLCM | ON THE LEVEL CARPENTRY & MILLWORK | | | SCAC4 |
| 1772 | OLCN | OIL CENTRAL INC | | | SCAC4 |
| 1773 | OLCT | O-LAND CONTAINER TRANSPORT INC | | | SCAC3 |
| 1774 | OLCU | OILCORE UAB | | LT | BIC |
| 1775 | OLCY | ORTHMAN LOGISTICS COMPANY | | | SCAC4 |
| 1776 | OLD | Beijing Orenda Tribe General Aviation Co., Ltd. | Callsign: Air Orenda, | PRC | AVCODES |
| 1777 | OLDB | OLD BAY TRANSFER | | | SCAC3 |
| 1778 | OLDB | OLD BLACKSMITH SHOP, THE | | | SCAC4 |
| 1779 | OLDC | OLD COLONY FILM TRANSFER CORP | | | SCAC3 |
| 1780 | OLDE | OLD DUTCH EXPRESS INC | | | SCAC3 |
| 1781 | OLDE | OLDE TOWN EXPRESS | | | SCAC4 |
| 1782 | OLDH | OLDHAM, JAY F AND SON, INC | | | SCAC3 |
| 1783 | OLDH | OLDHAM, JAY F AND SON, INC | | | SCAC4 |
| 1784 | OLDHCT | Oldham Corporation Passenger Transport | | GB | TRAFFIC |
| 1785 | OLDI | OLD IRON | | | SCAC4 |
| 1786 | OLDJ | OLDHAM, JACK OIL INC | | | SCAC4 |
| 1787 | OLDK | O L D TRUCKING | | | SCAC3 |
| 1788 | OLDK | OLDENKAMP TRUCKING | | | SCAC4 |
| 1789 | OLDL | OLDLAND DISTRIBUTING | | | SCAC3 |
| 1790 | OLDO | OLDOVER CORPORATION | | | SCAC3 |
| 1791 | OLDOP | OLOMOUCKÁ DOPRAVNI s.r.o. | | CZ | VKM |
| 1792 | OLDP | OLD SCHOOL EXPRESS | | | SCAC4 |
| 1793 | OLDQ | OLD DOMINION STEVEDORING CO | | | SCAC3 |
| 1794 | OLDR | OLD RELIABLE TRANSPORT INC | | | SCAC3 |
| 1795 | OLDR | OLD RELIABLE TRANSPORT INC | | | SCAC4 |
| 1796 | OLDS | OLD SOUTH FREIGHT SERVICE INC | | | SCAC3 |
| 1797 | OLDS | OLIVER, L D SEED CO INC | | | SCAC4 |
| 1798 | OLDT | OLD SOUTH TRANSPORTATION CO INC | | | SCAC3 |
| 1799 | OLDW | OLD WEST HARDWARE | | | SCAC4 |
| 1800 | OLDX | Old Line Holding Co., Inc. | added 1/1992; 1/1994-7/2000; eliminated 10/2004; 7/2005 (not listed) | | NAKINA |
