please correct

Dear Ramah,

I know that you are flying to Australia in September and do you know anybody or somebody flyinf from Sydney to Sri Lanka, if you can please let me know

Yours Sincerly
Ganesh

Dear Ramah,

I know that you will be flying to Australia in September and wondered if you knew anyone who will be flying from Sydney to Sri Lanka? If you do, please let me know.

Yours Sincerely,
Ganesh

My try

I know that you are flying to Australia in September.
Do you by chance know anybody who was to/should fly from Sydney to Sri Lanka?
If so please let me know.

Not a bad attempt, E2, but your verb choices was to/should are wrong.

These are the correct possibilities:
who is to fly
who will be flying
who is flying
who would be flying

How could I be sure he is to fly, still?

Thanks

You can’t. You’d have to ask that as a separate question closer to the time.