YOU SAID:

In an airplane, I was flying

INTO JAPANESE

飛行機の中で、私は飛んでいた

BACK INTO ENGLISH

I was flying on the plane

INTO JAPANESE

私は飛行機に乗っていました

BACK INTO ENGLISH

i was on a plane

INTO JAPANESE

私は飛行機に乗っていました

BACK INTO ENGLISH

i was on a plane