| Chicago to Olivares | 4,180.36 mi (6,727.63 km) |
| Chicago to Olivenza | 4,090.30 mi (6,582.70 km) |
| Chicago to Olot | 4,387.39 mi (7,060.82 km) |
| Chicago to Onate | 4,145.15 mi (6,670.97 km) |
| Chicago to Onda | 4,352.41 mi (7,004.52 km) |
| Chicago to Onteniente | 4,380.63 mi (7,049.94 km) |
| Chicago to Orihuela | 4,393.63 mi (7,070.87 km) |
| Chicago to Osuna | 4,235.86 mi (6,816.96 km) |
| Chicago to Ourense | 3,929.37 mi (6,323.71 km) |
| Chicago to Oviedo | 3,984.43 mi (6,412.32 km) |
| Chicago to Paiporta | 4,365.91 mi (7,026.25 km) |
| Chicago to Pajara | 4,136.39 mi (6,656.88 km) |
| Chicago to Palafolls | 4,418.29 mi (7,110.54 km) |
| Chicago to Palafrugell | 4,426.30 mi (7,123.45 km) |
| Chicago to Palamos | 4,427.62 mi (7,125.56 km) |
