Airlines have different policies about pregnancy, so there's no universal cut
off date but many are reluctant to carry women more than 32 weeks pregnant. However
they might ask for a note from your doctor saying that you are fit to fly. Remember
that your ticket agents won't ask if you're pregnant when you book the flight
tickets. Hence it's up to you to tell them, so check at that stage what the policy
of the airline is regarding pregnancy.
that will help you while traveling during pregnancy