I'm going to Japan next summer, and the cheapest flight by far is 15 hours from where I am to Shanghai, a 4 hour layover (which I know will be censored), and a 3 hour flight to Tokyo (which doesn't have internet in the first place). Will I have to get a VPN if I want to do my normal internet use on the first flight?
Apparently the sign in process on board is very convoluted, so you may wish to familiarise yourself with that first, as it may require registering in advance ;)
However, from the same review:
the typical “great firewall of China” also applies on China Eastern, as you’d expect.
So yes, you will run into limitations.