I saw something flying today. What should I call it in English?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
bytebuster has the provided the correct term, although I would parenthesize it like this: (hot air) balloon. That is, these objects can simply be called balloons, or hot-air balloons if you want to be more specific.
Hot air balloons belong to the family of flying machines called aerostats, or lighter-than-air flying aircraft. However, it should be noted that I've added that hypernym simply for reference purposes; the word aerostat is a more technical term that's seldom heard in day-to-day speech. In conversation, I'd expect to hear something more like:
Blimps and hot-air balloons are lighter-than-air aircraft.