if i want to travel from US to Australia in the omer can i fly to asia or do i have to fly around the world funly enough the flight on paper doesn’t miss a day im not sure why the flight proposed is vancouver (CAN), shanghi, melbourne AUS Do we have to fly around the world or is this flight good enough?
Flying from the US to Australia usually involves having an extra day, and not missing a day.
For the extra day one should count the same day again, without a berachah, and then continue to count with a berachah.
Nonetheless, it is preferable to avoid this situation if possible.
The main halachic authority that discusses this (and similar) question is Shut Betzel Ha-Chochmah (96-98).
If flying will involve missing or gaining a day of the Omer, you should preferably avoid doing so, as ruled there, and also by Rav Chaim Kanievsky.