| Chicago to Orbetello | 4,739.04 mi (7,626.75 km) |
| Chicago to Oria | 5,080.43 mi (8,176.17 km) |
| Chicago to Oristano | 4,737.52 mi (7,624.31 km) |
| Chicago to Orta Nova | 4,967.00 mi (7,993.62 km) |
| Chicago to Orte | 4,785.27 mi (7,701.15 km) |
| Chicago to Ortona | 4,870.06 mi (7,837.60 km) |
| Chicago to Orvieto | 4,763.22 mi (7,665.66 km) |
| Chicago to Orzinuovi | 4,565.22 mi (7,347.01 km) |
| Chicago to Osimo | 4,784.74 mi (7,700.29 km) |
| Chicago to Ospitaletto | 4,564.37 mi (7,345.65 km) |
| Chicago to Ostuni | 5,067.80 mi (8,155.84 km) |
| Chicago to Ottaviano | 4,939.21 mi (7,948.89 km) |
| Chicago to Ovada | 4,545.14 mi (7,314.70 km) |
| Chicago to Ozieri | 4,726.38 mi (7,606.37 km) |
| Chicago to Paceco | 4,986.66 mi (8,025.26 km) |
