| Keystone to Smolyan | 5,755.05 mi (9,261.86 km) |
| Keystone to Sofia | 5,654.87 mi (9,100.64 km) |
| Keystone to Sopot | 5,718.18 mi (9,202.52 km) |
| Keystone to Sozopol | 5,853.04 mi (9,419.56 km) |
| Keystone to Sredets | 5,834.37 mi (9,389.50 km) |
| Keystone to Stamboliyski | 5,727.66 mi (9,217.78 km) |
| Keystone to Stara Zagora | 5,764.92 mi (9,277.74 km) |
| Keystone to Svilengrad | 5,813.54 mi (9,355.99 km) |
| Keystone to Svishtov | 5,708.33 mi (9,186.67 km) |
| Keystone to Targovishte | 5,774.10 mi (9,292.52 km) |
| Keystone to Teteven | 5,687.64 mi (9,153.37 km) |
| Keystone to Troyan | 5,708.22 mi (9,186.49 km) |
| Keystone to Tryavna | 5,742.40 mi (9,241.50 km) |
| Keystone to Tutrakan | 5,745.38 mi (9,246.29 km) |
| Keystone to Varna | 5,831.35 mi (9,384.66 km) |
