Just wanted to know if it was possible to power up a raspberry pi 3 (+7'' touch screen) from the USB socket you can find next to the screen in a plane. I have no idea how much power they provide...
yes you can, but the pi will be unstable(it may reboot on it's own), I have been powering the pi from my 0.5A USB port in my laptop, and it was smooth and reliable.
P.S. my pi is 3B
When I travel I Power Pi’s using a usb power bank. Although this works with an LCD screen, will probably drain the battery quite quickly. As you can see from the pic though, it does work. However, be aware you can't take huge USB battery banks on the plane with security restrictions being what they are. I had a 26,0000 MaH taken off me at the airport in Istanbul. The size shown is OK to get through security from my experience. Touch screen in pic is used with a 3B+
Anyhoo, an alternative power solution to working with Pis while traveling that I've used-