Policies vary between airlines, so it is best to ask about restrictions when booking your flight. It is generally accepted that you can fly during the first and second trimesters of pregnancy. Please note, airlines can prevent travel if they are worried about how far along in your pregnancy you are. To avoid any issues, it is recommended that you get written permission to fly from your doctor or midwife. The letter should confirm your due date and state that you have been examined and are not likely to go into labour within the next 72 hours.