| Port Huron to Orbetello | 4,477.67 mi (7,206.11 km) |
| Port Huron to Oria | 4,821.92 mi (7,760.13 km) |
| Port Huron to Oristano | 4,470.67 mi (7,194.84 km) |
| Port Huron to Orta Nova | 4,707.91 mi (7,576.65 km) |
| Port Huron to Orte | 4,524.92 mi (7,282.15 km) |
| Port Huron to Ortona | 4,611.31 mi (7,421.18 km) |
| Port Huron to Orvieto | 4,503.02 mi (7,246.91 km) |
| Port Huron to Orzinuovi | 4,307.48 mi (6,932.23 km) |
| Port Huron to Osimo | 4,526.94 mi (7,285.40 km) |
| Port Huron to Ospitaletto | 4,307.02 mi (6,931.48 km) |
| Port Huron to Ostuni | 4,809.58 mi (7,740.27 km) |
| Port Huron to Ottaviano | 4,678.30 mi (7,529.00 km) |
| Port Huron to Ovada | 4,285.09 mi (6,896.19 km) |
| Port Huron to Ozieri | 4,460.69 mi (7,178.79 km) |
| Port Huron to Paceco | 4,720.38 mi (7,596.72 km) |
