〜前まで回復するって英語でなんて言うの？

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！