| Northolt to Orbetello | 831.01 mi (1,337.39 km) |
| Northolt to Oria | 1,147.00 mi (1,845.92 km) |
| Northolt to Oristano | 911.52 mi (1,466.96 km) |
| Northolt to Orta Nova | 1,037.20 mi (1,669.21 km) |
| Northolt to Orte | 866.74 mi (1,394.88 km) |
| Northolt to Ortona | 939.70 mi (1,512.30 km) |
| Northolt to Orvieto | 844.05 mi (1,358.38 km) |
| Northolt to Orzinuovi | 633.83 mi (1,020.06 km) |
| Northolt to Osimo | 850.91 mi (1,369.41 km) |
| Northolt to Ospitaletto | 630.99 mi (1,015.48 km) |
| Northolt to Ostuni | 1,133.35 mi (1,823.95 km) |
| Northolt to Ottaviano | 1,021.12 mi (1,643.34 km) |
| Northolt to Ovada | 632.24 mi (1,017.49 km) |
| Northolt to Ozieri | 879.04 mi (1,414.67 km) |
| Northolt to Paceco | 1,127.68 mi (1,814.82 km) |
