YOU SAID:

if you are going to a concert today then you should not eat any food on the flight

INTO JAPANESE

今日コンサートに行くなら、飛行機の中で食べ物を食べてはいけません

BACK INTO ENGLISH

If you go to a concert today, don't eat food on the plane

INTO JAPANESE

今日コンサートに行くなら、飛行機の中で食べ物を食べないでください

BACK INTO ENGLISH

If you go to a concert today, don't eat food on the plane