| Hartford to Orbetello | 4,108.85 mi (6,612.56 km) |
| Hartford to Oria | 4,461.14 mi (7,179.51 km) |
| Hartford to Oristano | 4,080.80 mi (6,567.42 km) |
| Hartford to Orta Nova | 4,345.81 mi (6,993.91 km) |
| Hartford to Orte | 4,159.49 mi (6,694.05 km) |
| Hartford to Ortona | 4,251.01 mi (6,841.34 km) |
| Hartford to Orvieto | 4,138.29 mi (6,659.93 km) |
| Hartford to Orzinuovi | 3,952.76 mi (6,361.36 km) |
| Hartford to Osimo | 4,170.48 mi (6,711.74 km) |
| Hartford to Ospitaletto | 3,953.63 mi (6,362.76 km) |
| Hartford to Ostuni | 4,449.90 mi (7,161.42 km) |
| Hartford to Ottaviano | 4,309.96 mi (6,936.21 km) |
| Hartford to Ovada | 3,922.31 mi (6,312.34 km) |
| Hartford to Ozieri | 4,075.56 mi (6,558.99 km) |
| Hartford to Paceco | 4,331.54 mi (6,970.95 km) |
