| Prospect Heights to Olivares | 4,183.57 mi (6,732.80 km) |
| Prospect Heights to Olivenza | 4,093.21 mi (6,587.39 km) |
| Prospect Heights to Olot | 4,387.28 mi (7,060.65 km) |
| Prospect Heights to Onate | 4,145.58 mi (6,671.66 km) |
| Prospect Heights to Onda | 4,353.60 mi (7,006.44 km) |
| Prospect Heights to Onteniente | 4,382.29 mi (7,052.61 km) |
| Prospect Heights to Orihuela | 4,395.62 mi (7,074.07 km) |
| Prospect Heights to Osuna | 4,238.94 mi (6,821.92 km) |
| Prospect Heights to Ourense | 3,930.98 mi (6,326.31 km) |
| Prospect Heights to Oviedo | 3,985.30 mi (6,413.72 km) |
| Prospect Heights to Paiporta | 4,367.32 mi (7,028.52 km) |
| Prospect Heights to Pajara | 4,144.44 mi (6,669.83 km) |
| Prospect Heights to Palafolls | 4,418.31 mi (7,110.59 km) |
| Prospect Heights to Palafrugell | 4,426.17 mi (7,123.23 km) |
| Prospect Heights to Palamos | 4,427.52 mi (7,125.40 km) |
