Lot's of good advice about what to do during flights above.
This pregnancy I have flown to 6 different countries, {some of them twice}, for work and pleasure. I have done 3 long haul flights , my last one at 6 months.
I have found the flying and travelling to be easy while pregnant at all stages.
The research I have done shows that the radiation in commercial planes is not harmful to you or your baby.
Here is a pretty good website about the radiation side of things:
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The really important thing though, that I wanted to add, is what 'mum of 2' referred to above. Think hard about where you are travelling to and who you will have with you for support.
Unfortunately my first pregnancy ended in miscarriage, after a flight to Shenyang {in far north China} for work. There was nothing about the flight or my travel that caused the miscarriage, but the consequences were that I had it alone in essentially a third world hospital, in appalling conditions, a long way from home {it took me 24 hours to get back here for treatment.} I have 'flash backs' and nightmares about it to this day.
Needless to say, this pregnancy, with all of the flying I mentioned above, I have been with my partner, or going to big cities with international standard hospitals, when travelling alone for work.
I think your holiday to Bali sounds like a great idea. We went there when I was about about 20 weeks pregnant for our 'baby moon'. Enjoy your holiday.