| Duncan to Smolyan | 6,043.50 mi (9,726.07 km) |
| Duncan to Sofia | 5,939.27 mi (9,558.33 km) |
| Duncan to Sopot | 5,992.25 mi (9,643.59 km) |
| Duncan to Sozopol | 6,106.51 mi (9,827.47 km) |
| Duncan to Sredets | 6,092.77 mi (9,805.37 km) |
| Duncan to Stamboliyski | 6,010.22 mi (9,672.51 km) |
| Duncan to Stara Zagora | 6,034.72 mi (9,711.95 km) |
| Duncan to Svilengrad | 6,087.60 mi (9,797.04 km) |
| Duncan to Svishtov | 5,965.00 mi (9,599.73 km) |
| Duncan to Targovishte | 6,025.84 mi (9,697.65 km) |
| Duncan to Teteven | 5,961.96 mi (9,594.84 km) |
| Duncan to Troyan | 5,979.48 mi (9,623.04 km) |
| Duncan to Tryavna | 6,007.73 mi (9,668.51 km) |
| Duncan to Tutrakan | 5,986.43 mi (9,634.22 km) |
| Duncan to Varna | 6,072.77 mi (9,773.18 km) |
