TIP: Since Google Flights Explorer is broken, go to the regular Google Flight search at:
https://www.google.ca/flights/
- Enter in the city (Hong Kong, Seoul, or Tokyo)
- Pick some random dates. Doesn't matter what dates, but make it the same length of time that you are thinking of going.
- Click on the little bar graph icon. It's on the right, above the blue line.
- This will bring up a monthly calendar view. Scroll through the months. It will show you date combinations that *may* still be available. Hover over dates to see them.
- Take one of these date combinations and try it directly on Delta.com
It's hard to say how accurate a reflection Google's data is of the real availability on Delta.com, but it's a good way to explore large numbers of date combos at once.