I think it depends on how your pregnancy has progressed, how you are and if you feel you are up to an 8/10 hour plus flight each way with possible delays, sitting round etc. Your MW is best to advise on all that. You may be fine now, but develop a small problem in a few weeks that would mean she would advise against it.
I wasn't that big at 20 weeks but by 23 I had a farily large bump and found sitting for too long in one position/chair uncomfy. I'd have flown a couple of hours, but I'd personally not want to sit long haul at that point. But others are happy to do so. The airport waiting, check in 2 hours ahead and all that would do for me. I just could not have coped with all that plus a long flight.
There are increased risks when flying during pregnancy. I am sure your MW will explain and about how much of an increase it actually is.
Keeping hydrated, moving around, wearing flight socks etc would all be good to do.
Also consider as has been said medical insurance. You should get this if PG and going away in case anything happens while overseas. Even something as simple as drinking some iffy water could make you ill and give you the runs and dehydrate you etc. Not good for LO or you. Hard to know when you go overseas as to the standards of care given also.