Maybe the inverse is what is needed? I'd like to know what is bookable at all.

I've been looking at Asia-Australia routes a long way out (late March 2018) just as a test. United shows up to 200 possibilities for single dates. (e.g. PVG-SYD) They include a bit of the next day as well in their results when it's an early am departure, so it's really a little less, but it also doesn't include any SQ options that would have to be booked by phone. LM shows mostly no options at all. Some days, maybe one or two, sometimes with mixed class, mostly on routes I wouldn't want or on NH, which others have reported may fail to book anyhow!