| Alpena to Smolyan | 4,989.52 mi (8,029.86 km) |
| Alpena to Sofia | 4,885.36 mi (7,862.23 km) |
| Alpena to Sopot | 4,939.14 mi (7,948.78 km) |
| Alpena to Sozopol | 5,055.51 mi (8,136.05 km) |
| Alpena to Sredets | 5,041.25 mi (8,113.10 km) |
| Alpena to Stamboliyski | 4,956.55 mi (7,976.80 km) |
| Alpena to Stara Zagora | 4,982.04 mi (8,017.83 km) |
| Alpena to Svilengrad | 5,034.70 mi (8,102.56 km) |
| Alpena to Svishtov | 4,913.30 mi (7,907.20 km) |
| Alpena to Targovishte | 4,974.79 mi (8,006.15 km) |
| Alpena to Teteven | 4,908.77 mi (7,899.90 km) |
| Alpena to Troyan | 4,926.56 mi (7,928.54 km) |
| Alpena to Tryavna | 4,955.37 mi (7,974.89 km) |
| Alpena to Tutrakan | 4,936.41 mi (7,944.39 km) |
| Alpena to Varna | 5,022.98 mi (8,083.71 km) |
