Help me with some preposition.

[lucas_araujo_22]

I have a doubt about these preposition: on , in.
Thus I made 2 sentences practicing it. Tell me whether they are correct.

We're booked ON flight 607
He wrote the book in a month's time.

Thank u.

[5jj]

We're booked ON flight 607.
He wrote the book in a month's time.= The writing took one month.

Thank you.

He will start writing the book in a month's time = a month from now, in the future.

'In' is correct in all these sentences.

[lucas_araujo_22]

Thank you a lot .