I just did a quick search and it seems that Netflix does not allow offline watching on tablets or phones. The reason they give is ludicrous - apparently they believe that it adds a layer of complexity that most consumers won't want. OK then...
However the good news is that Amazon Prime
does allow offline viewing on mobile devices. While this was originally limited to their Fire tablets, you can now watch offline on any Android or iOS device.
Personally I got rid of Netflix ages ago once I realized that my Amazon Prime subscription offers video streaming as well. I know there's stuff on Netflix that's not on Amazon Prime, but I haven't been bothered by this yet. It seems that most everything I want to watch is on there.