Week 11 is it safe to take 13 hour flight

At 11 weeks pregnant, a 13-hour flight is generally considered okay by most doctors, but honestly it's quite long and the risk of blood clots goes up with prolonged sitting, so it really depends on your individual pregnancy and health. I'd say check with your gynae first because they know your situation best and can give you the green light or suggest precautions like compression socks or getting up to walk around every couple of hours. Most airlines also have their own policies on how far along you can fly, so worth checking with Lufthansa or whoever you're flying with too.