I think the number of flights will recover to where they were pre-COVIDin a few years.
I'm guessing the number of flights will bounce back to the way they were before COVID in a few years.
この場合、次のような言い方ができますよ。
ーI think the number of flights will recover to where they were pre-COVID in a few years.
「あと数年で、飛行機の本数はコロナ前まで回復すると思います」
to recover to where they were pre-COVID を使った言い方。
ーI'm guessing the number of flights will bounce back to the way they were before COVID in a few years.
「あと数年で、飛行機の本数はコロナ前まで回復するでしょう」
to bounce back to the way they were before COVID を使った言い方。
ご参考まで！
カナダ 
