Yes generally safe. But nausea and exhaustion will make flying uncomfy. There is a higher chance of dvt risk since this is a long haul. (Anything more than 4 hours have higher risk): so make sure you get compression socks, walk the aisle every hour, drink lots of water as cabin air is very dry and wear your seatbelt low across the upper thigh and not your abdomen. Do also ankle exercises while seated. Flex then, rotate them etc. Enjoy germany!!