I have travelled out of USA and between cities with 2 consoles on carry on with no problem. And since (but I had to take out to screen out). But since some aircrafts have power outlets and av in (maybe even hdmi) you could even play it as long as you don't enable blutooth.

You'll have no problem getting a 3DS on there Wii U I don't think you should

I brought my 3DS on the plane last month, that was a national flight in the USA though, so it might be different elsewhere.

I know someone that has flown with both a Wii U and a 3DS, domestically in the US and internationally. Just let them scan the console individually if you are worried. They might ask questions, so just answer honestly. It really depends on that airport though.

Game handhelds are no problem, you don't even have to take those out of the bag from my experience. Flown with both my 3DS and Vita multiple times. Wii U you will probably have to take it out of your carry on to be scanned like a laptop. I reccomend if you're doing that that you get to the airport 10-15 minutes earlier than usual because someone might make a fuss about it and ask you to plug it in and what not. 

You don't want to miss your flight because you ended up taking 10-15 minutes longer through security. 

I've flown internationally between US and Japan a number of times with 3ds, portable battery, laptop, PS4/WII U in my carry ons and have never had to take anything out except for my Laptop, but it may depend on the airport.

That reminds me of a funny story... When they scanned my Wii U, one security guy didn't even know what it was. He recognized the 360 but he said he'd never seen or even heard of a Wii U before. lol Then he was thinking of calling his supervisor but I showed him the Wii Us box and he let me go. 

I love that image so much.

there is a guy playing Wii U on a plane but I cant find the video all youtube shows me is this garbage cgi plane cartoon.

thats it