Third trimester questions please read?

How often should I get an appointment? I went it at 28 weeks pregnant and got an appointment for a month later.. I read that I should get one every 2 weeks is that true? And also I will be flying international (14hrs) when I'm about 34 weeks pregnant I asked one of my doctors if it was okay to fly and he said Yes until 36 weeks.. I get a different doctor every visit because that's how it works here :( anyway I haven't had any complications so would it be ok? I will ask my dr but I don't have an appointment until the 15 of July.. I'm 30 weeks pregnant