| South Houston to Smolyan | 6,201.93 mi (9,981.03 km) |
| South Houston to Sofia | 6,098.41 mi (9,814.44 km) |
| South Houston to Sopot | 6,155.35 mi (9,906.08 km) |
| South Houston to Sozopol | 6,277.50 mi (10,102.66 km) |
| South Houston to Sredets | 6,261.98 mi (10,077.68 km) |
| South Houston to Stamboliyski | 6,170.49 mi (9,930.44 km) |
| South Houston to Stara Zagora | 6,199.60 mi (9,977.29 km) |
| South Houston to Svilengrad | 6,251.36 mi (10,060.59 km) |
| South Houston to Svishtov | 6,133.92 mi (9,871.59 km) |
| South Houston to Targovishte | 6,196.87 mi (9,972.90 km) |
| South Houston to Teteven | 6,124.77 mi (9,856.86 km) |
| South Houston to Troyan | 6,143.47 mi (9,886.96 km) |
| South Houston to Tryavna | 6,173.97 mi (9,936.05 km) |
| South Houston to Tutrakan | 6,160.82 mi (9,914.89 km) |
| South Houston to Varna | 6,247.64 mi (10,054.60 km) |
