Was trying to book HND-SFO and called the GS line. Could not get the option to come up on ual.com. IAH agent very politely told me the reason is that flights from Haneda are all domestic and I was trying to fly international.

Asked for a supervisor's help who also could not book it even though they could see the flight and there seemed to be inventory in my fare class, Z. Original agent apologized and said her supervisor figured out that the flight is "only for the Japanese". double Gave up and booked from NRT.