I frequently travel throughout Europe with my drone(s). I checked the procedures carefully before I travel, but I've not had any major problems.
It varies from airline to airline, but for most of the EU, you can carry up to four LIPO
batteries under 100 watt hours (For me, this is three Mavic 2/
Spark batteries and my 21mAh phone pack.) in your hand baggage, NOT checked-in.
It is recommended that you discharge any
batteries you will not be using to below 25% and make sure they cannot short. I use camkix LIPO explosion proof bags for mine.
On going through security, I put the drone, the controller and all its
batteries in the electronics tray and declare the lot as carry-on baggage.
I've been stopped twice while travelling with a drone. The first time I ever travelled with a drone, I got stopped and pulled aside because...I had a 50ml container of hand gel in my sponge bag I had forgotten about. The security guy also said 'Hey, is that a Spark? I own a Phantom!'. We ended up happily geeking out about drones while he checked my hand luggage.
The second time I got stopped because the security dude was unfamiliar with LiPo explosion-proof bags. I explained what they were (never use the word 'explosion' to airport security- I saw the poor man flinch!), and he took the
batteries out and swabbed the bag and they went through no problem.
Other than those two instances, I've had no issues. I guess I'd have avoided the second one if I hadn't used the explosion proof bags, but I feel they are a suitable extra layer of safety and best practice when travelling with high-voltage
batteries. The most common reaction I've had is a certain amount of drooling and quite a few chats with drone-owning security guards or passengers. I realised that a lot of folks get jobs at airport due to a general fascination with anything airborne, so normally they are friendly and interested...and a little bit envious!