| Houston to Smolyan | 6,201.57 mi (9,980.46 km) |
| Houston to Sofia | 6,098.01 mi (9,813.80 km) |
| Houston to Sopot | 6,154.81 mi (9,905.21 km) |
| Houston to Sozopol | 6,276.67 mi (10,101.32 km) |
| Houston to Sredets | 6,261.21 mi (10,076.45 km) |
| Houston to Stamboliyski | 6,170.05 mi (9,929.74 km) |
| Houston to Stara Zagora | 6,198.99 mi (9,976.32 km) |
| Houston to Svilengrad | 6,250.80 mi (10,059.70 km) |
| Houston to Svishtov | 6,133.15 mi (9,870.35 km) |
| Houston to Targovishte | 6,196.02 mi (9,971.54 km) |
| Houston to Teteven | 6,124.23 mi (9,856.00 km) |
| Houston to Troyan | 6,142.89 mi (9,886.03 km) |
| Houston to Tryavna | 6,173.31 mi (9,934.98 km) |
| Houston to Tutrakan | 6,159.84 mi (9,913.31 km) |
| Houston to Varna | 6,246.65 mi (10,053.01 km) |
