Look at the helicopters! There are three of them.(ヘリコプターを見て!3機もあるよ)
I wonder if we can see anybody in there.(誰か中にいるか見えるかな)
They are gone now.(もう行っちゃったね)
「あっ、ヘリコプターだ」は次のような言い方ができます。
ーOh look! There's a helicopter.
ーThere's a helicopter up there.
例:
Oh look! There's a helicopter. There are three helicopters flying today. We usually only see one or two. I wonder who's in those helicopters. I can't see them anymore. I guess they went somewhere.
「あっ、ヘリコプターだ。今日は3機飛んでるよ。いつもは1機か2機なのにね。誰が乗ってるんだろう。見えなくなっちゃった。どこか行っちゃったんだね」
ご参考まで!