The guide book probably factored in the transit time from Tokyo to Narita in the 4 hour figure.
I, too, aim to arrive at the airport 2 hours before the departure time. Less if you can OLCI and bypass the check-in queue. As an aside, what airlines operating in Narita support OLCI?
In the past, I have seen UA Y check in agents holding up signs with flight numbers that are close to departure time. If you are on one of those flights, the check in agent will lead you to the front of the queue.
Last edited by msb0b; Jun 30, 2014 at 11:58 am
Reason: typo