| Hartford to Oerlinghausen | 3,701.71 mi (5,957.33 km) |
| Hartford to Oestrich-Winkel | 3,730.62 mi (6,003.85 km) |
| Hartford to Offenburg | 3,772.66 mi (6,071.51 km) |
| Hartford to Oftersheim | 3,772.63 mi (6,071.46 km) |
| Hartford to Ohrdruf | 3,815.42 mi (6,140.33 km) |
| Hartford to Ohringen | 3,814.93 mi (6,139.53 km) |
| Hartford to Olbernhau | 3,922.23 mi (6,312.22 km) |
| Hartford to Olching | 3,919.97 mi (6,308.58 km) |
| Hartford to Oldenburg | 3,652.36 mi (5,877.91 km) |
| Hartford to Oldenburg in Holstein | 3,721.71 mi (5,989.52 km) |
| Hartford to Olfen | 3,658.22 mi (5,887.33 km) |
| Hartford to Olpe | 3,695.22 mi (5,946.88 km) |
| Hartford to Olsberg | 3,711.67 mi (5,973.36 km) |
| Hartford to Oranienburg | 3,854.10 mi (6,202.57 km) |
| Hartford to Ortenberg | 3,762.77 mi (6,055.59 km) |
