It’s absolutely safe to fly throughout most of your pregnancy.

If this is your first baby, now’s your chance to enjoy the luxury of uninterrupted time alone, with your partner or with friends. It’s also a last opportunity to make the most of travelling light. For the next few years, you’ll have to take a car seat, pushchair, nappies and toys with you wherever you go!

Follow our tips for a relaxing and safe flight.
Is it safe to fly during my first and second trimesters?
Yes, but check with your doctor before flying if you’ve had medical problems during your pregnancy such as:

spotting
diabetes
high blood pressure
excessive morning sickness (hyperemesis gravidarum)
a previous miscarriage
a previous early birth

You may find your second trimester (14 weeks to 27 weeks) is the best time to fly. If you’ve had morning sickness, it should hopefully be behind you by then. In addition, your energy levels will be higher and your hormones will be giving you a boost, so you’ll be looking and feeling great.

Read more on https://www.babycentre.co.uk/a6955/flying-while-pregnant