Flying is not harmful, however airlines often won’t let you fly in late pregnancy. Also long distance (longer than 5 hours) carries a risk albeit small of thrombosis (blood clots) in pregnant women. Discuss your plans with your Doctor who may prescribe aspirin or heparin.
If you are flying drink plenty of water, do calf exercises and walk on the flight, wear support stockings. And importantly think about where you are flying to…..could you get medical help if needed, are there any vaccinations needed which may be harmful to a pregnancy. Road traffic accidents tend to be the more common injuries pregnant women sustain during a pregnancy, remember to wear the seatbelt above and below the bump but not over or across it.