Japan Airlines (JAL) has a tool to check availability on their own operated flights. Just note you’ll need to sign up for the JAL Mileage Bank program and login before you can access it. For HKG based travelers JAL is a great partner for Asia Miles and Oneworld. You can fly not only to Japan, but if you don’t mind connecting through Tokyo, many international destinations in Europe or the US as well. Additionally, Asia Miles will even allow a free stopover along the way.
The JAL tool is pretty good if you know how to use it. For example, if you’re flying Tokyo to New York, you can use the calendar search to check what days seats are available that week. One interesting feature is that you can search all cities in a certain region, so in North America you can see LAX, SFO, YVR, ORD, JFK, BOS, etc. This is great, because if seats to JFK are gone, you can still check if there’s seats to another city and book a domestic flight on AA to get to JFK.
To access this tool, once you login with your Mileage Bank account information, a page will come up and click the link saying “International award ticket reservation.”
My main gripe with JAL involves Asia Miles, you CANNOT book a one-way award ticket, must be roundtrip. If you use AAdvantage Miles or British Airways Avios however, you can book a one-way which I think is weird. It appears an Asia Miles rule rather than JAL rule.