| West Chicago to Orbetello | 4,758.19 mi (7,657.57 km) |
| West Chicago to Oria | 5,098.98 mi (8,206.01 km) |
| West Chicago to Oristano | 4,757.87 mi (7,657.05 km) |
| West Chicago to Orta Nova | 4,985.67 mi (8,023.66 km) |
| West Chicago to Orte | 4,804.21 mi (7,731.63 km) |
| West Chicago to Ortona | 4,888.67 mi (7,867.55 km) |
| West Chicago to Orvieto | 4,782.13 mi (7,696.09 km) |
| West Chicago to Orzinuovi | 4,583.66 mi (7,376.69 km) |
| West Chicago to Osimo | 4,803.17 mi (7,729.96 km) |
| West Chicago to Ospitaletto | 4,582.74 mi (7,375.21 km) |
| West Chicago to Ostuni | 5,086.29 mi (8,185.59 km) |
| West Chicago to Ottaviano | 4,958.25 mi (7,979.53 km) |
| West Chicago to Ovada | 4,564.05 mi (7,345.12 km) |
| West Chicago to Ozieri | 4,746.46 mi (7,638.69 km) |
| West Chicago to Paceco | 5,006.86 mi (8,057.76 km) |
