| Dayton to Orbetello | 4,682.66 mi (7,536.02 km) |
| Dayton to Oria | 5,029.98 mi (8,094.97 km) |
| Dayton to Oristano | 4,667.73 mi (7,511.99 km) |
| Dayton to Orta Nova | 4,915.42 mi (7,910.61 km) |
| Dayton to Orte | 4,731.12 mi (7,614.00 km) |
| Dayton to Ortona | 4,819.30 mi (7,755.92 km) |
| Dayton to Orvieto | 4,709.43 mi (7,579.10 km) |
| Dayton to Orzinuovi | 4,516.91 mi (7,269.26 km) |
| Dayton to Osimo | 4,736.07 mi (7,621.97 km) |
| Dayton to Ospitaletto | 4,516.86 mi (7,269.18 km) |
| Dayton to Ostuni | 5,017.99 mi (8,075.67 km) |
| Dayton to Ottaviano | 4,883.68 mi (7,859.52 km) |
| Dayton to Ovada | 4,491.91 mi (7,229.02 km) |
| Dayton to Ozieri | 4,659.64 mi (7,498.97 km) |
| Dayton to Paceco | 4,918.11 mi (7,914.93 km) |
