| Chicago to Oerlinghausen | 4,260.83 mi (6,857.14 km) |
| Chicago to Oestrich-Winkel | 4,310.45 mi (6,937.00 km) |
| Chicago to Offenburg | 4,366.44 mi (7,027.11 km) |
| Chicago to Oftersheim | 4,356.25 mi (7,010.71 km) |
| Chicago to Ohrdruf | 4,378.54 mi (7,046.58 km) |
| Chicago to Ohringen | 4,397.01 mi (7,076.31 km) |
| Chicago to Olbernhau | 4,477.79 mi (7,206.31 km) |
| Chicago to Olching | 4,504.52 mi (7,249.33 km) |
| Chicago to Oldenburg | 4,201.27 mi (6,761.29 km) |
| Chicago to Oldenburg in Holstein | 4,250.45 mi (6,840.44 km) |
| Chicago to Olfen | 4,223.82 mi (6,797.58 km) |
| Chicago to Olpe | 4,266.11 mi (6,865.64 km) |
| Chicago to Olsberg | 4,277.31 mi (6,883.67 km) |
| Chicago to Oranienburg | 4,390.37 mi (7,065.62 km) |
| Chicago to Ortenberg | 4,335.87 mi (6,977.90 km) |
