S31
S31 stands for:
- S-Bahn line 31 (Hamburg)
- S-Bahn line 31 (Styria)
- Burgenland Schnellstraße , an expressway in Austria
S.31 stands for:
- SPAD S.31 , a single-seat biplane aircraft made by the French manufacturer SPAD
Š-31 stands for:
- Letov Š-31 , a single-engine, single-seat biplane designed as a fighter aircraft
