I'm going travelling, and in case there wasn't super-duper wifi everywhere, I bought a 64gb Lexar OTG USB disk with a micro-usb2 connector on one side and a usb3 standard connector on the other. OMG! that was half a day to get it work on the Nexus 7-2. I don't even know what worked - using tware format on windows to format it to fat32 or multiple power offs. Finally it works, but you really have to eject it properly. When it works, android picks it up, and you can use any file explorer. You can put a lot of movies on it for the plane, and a lot of pictures.
It didn't do anything with the Nexus 5x no matter what I did.