| Port Code | Port Name | Country |
| USOSG | Oswego | United States |
| USOSH | Oshkosh | United States |
| USOSK | Woonsocket | United States |
| USOSL | Oslo | United States |
| USOSM | Selma | United States |
| USOSO | Rosholt | United States |
| USOSS | Ossining | United States |
| USOST | Ostrica | United States |
| USOSW | Oswego | United States |
| USOSX | Kosciusko | United States |
| USOSY | Old Saybrook | United States |
| USOTA | Cotton Plant | United States |
| USOTC | Monticello | United States |
| USOTD | Onsted | United States |
| USOTE | Montgomery | United States |
| USOTG | Worthington | United States |
| USOTH | North Bend | United States |
| USOTI | Port Norris | United States |
| USOTL | Ottawa Lake | United States |
| USOTM | Ottumwa | United States |
| USOTN | Oaktown | United States |
| USOTO | Otto | United States |
| USOTP | Orrtanna | United States |
| USOTQ | Ottawa | United States |
| USOTR | Ottawa | United States |
| USOTS | Anacortes | United States |
| USOTT | Cottonton | United States |
| USOTV | Scottsville | United States |
| USOTW | Ottawa | United States |
| USOTZ | Kotzebue | United States |
| USOUA | Mount Ayr | United States |
| USOUC | Council | United States |
| USOUD | Mound | United States |
| USOUF | Oakland | United States |
| USOUH | Southgate | United States |
| USOUI | Blountville | United States |
| USOUK | Mounds | United States |
| USOUL | South Charleston | United States |
| USOUM | Mount Meigs | United States |
| USOUN | Norman | United States |
| USOUO | Mount Morris | United States |
| USOUR | Ouray | United States |
| USOUT | Courtdale | United States |
| USOUV | Mount Vernon | United States |
| USOUY | South Yarmouth | United States |
| USOVA | Solvay | United States |
| USOVE | Oroville | United States |
| USOVI | Covington | United States |
| USOVL | Overland Park | United States |
| USOVR | Overpeck | United States |
| USOVW | Oroville | United States |
| USOVZ | Otwell | United States |
| USOWA | Owatonna | United States |
| USOWB | Owensboro | United States |
| USOWC | Welch | United States |
| USOWD | Norwood | United States |
| USOWE | Lowell | United States |
| USOWG | Owego | United States |
| USOWI | Owings Mills | United States |
| USOWK | Norridgewock | United States |
| USOWL | Bowling Green | United States |
| USOWN | Orrstown | United States |
| USOWO | Owosso | United States |
| USOWP | Orwigsburg | United States |
| USOWV | Owensville | United States |
| USOXA | Oxford | United States |
| USOXB | Oxford | United States |
| USOXC | Oxford | United States |
| USOXD | Oxford | United States |
| USOXF | Oxford | United States |
| USOXG | Oxford | United States |
| USOXK | Oakland Mills | United States |
| USOXL | Olin | United States |
| USOXN | Oxnard | United States |
| USOXO | Oxford | United States |
| USOXP | Newton | United States |
| USOXQ | Corunna | United States |
| USOXR | Oxnard-Ventura Apt | United States |
| USOXR | Ventura-Oxnard Apt | United States |
| USOXX | Oasis | United States |
| USOYB | Oyster Bay | United States |
| USOYD | Boyden | United States |
| USOYI | Oneida | United States |
| USOYS | Yosemite Ntl Park | United States |
| USOYT | Savoy | United States |
| USOZA | Ozona | United States |
| USOZI | Old Monroe | United States |
| USOZK | Ozark | United States |
| USOZO | Ozone Park/Queens/New York | United States |
| USOZR | Ozark | United States |
| USOZZ | Osseo | United States |
| USPAA | Pine Apple | United States |
| USPAB | Palm Beach | United States |
| USPAC | Park City | United States |
| USPAD | Paulding | United States |
| USPAE | Everett | United States |
| USPAF | Plainfield | United States |
| USPAG | Pisgah | United States |
| USPAH | Paducah | United States |
| USPAI | Paintsville | United States |