I was on a plane waiting for takeoff when the back of the plane caught fire.
"飛行機に乗って離陸を待っていたら後ろが火事になっていた"
- I was on a plane waiting for takeoff when the back of the plane caught fire.
- The back of the plane caught fire when I was on it waiting for takeoff.
- I was waiting for the plane to take off when the plane caught fire.
乗っている飛行機の後ろの方から煙が出ていて、火事でした。
- There was smoke coming from the back of the plane we were on and it was a fire.
I was riding on a place waiting for liftoff when suddenly the back of the plane caught on fire.
ご質問ありがとうございます。
この場合、「[飛行機](https://eikaiwa.dmm.com/uknow/questions/36261/)に乗って離陸を待っていたら後ろが火事になっていた」と言いたいなら、英語で「I was riding on a place waiting for liftoff when suddenly the back of the plane caught on fire.」と言えます。
ご参考になれば幸いです。
I was sitting on an airplane waiting to take off and a fire broke out at the back of the airplane.
この場合、次のような言い方ができますよ。
ーI was sitting on an airplane waiting to take off and a fire broke out at the back of the airplane.
「飛行機に乗って離陸するのを待っていたら、飛行機の後ろで火事が起こった」
to take off で「離陸する」
to break out で「（火事などが）起こる」
ご参考まで！
アメリカ合衆国 
カナダ 
