| Owings Mills to Oerlinghausen | 3,970.68 mi (6,390.19 km) |
| Owings Mills to Oestrich-Winkel | 4,000.33 mi (6,437.91 km) |
| Owings Mills to Offenburg | 4,042.61 mi (6,505.96 km) |
| Owings Mills to Oftersheim | 4,042.43 mi (6,505.67 km) |
| Owings Mills to Ohrdruf | 4,084.62 mi (6,573.56 km) |
| Owings Mills to Ohringen | 4,084.71 mi (6,573.71 km) |
| Owings Mills to Olbernhau | 4,191.15 mi (6,745.01 km) |
| Owings Mills to Olching | 4,189.82 mi (6,742.87 km) |
| Owings Mills to Oldenburg | 3,920.79 mi (6,309.90 km) |
| Owings Mills to Oldenburg in Holstein | 3,988.93 mi (6,419.56 km) |
| Owings Mills to Olfen | 3,927.44 mi (6,320.60 km) |
| Owings Mills to Olpe | 3,964.65 mi (6,380.49 km) |
| Owings Mills to Olsberg | 3,980.92 mi (6,406.67 km) |
| Owings Mills to Oranienburg | 4,121.93 mi (6,633.60 km) |
| Owings Mills to Ortenberg | 4,032.30 mi (6,489.36 km) |
