O1 or O-1 may refer to:
== Aircraft == Cessna O-1 Bird Dog, an observation aircraft manufactured by Cessna O-1 Curtiss Falcon, an observation aircraft manufactured by the Curtiss Aircraft Company O-1 Airship, an Italian manufactured semi-rigid airship operated by the US Navy
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).