Though Delta isn't known for offering a generous amount of
award space to its partners, I was able to
find four first - class
award seats available in August from Denver to Maui
via Los Angeles and Seattle using the online
award search engine for Alaska Airlines, which you don't even need an account to use.
There are a lot of tools available online that can help in
finding award space, but not all of them are robust enough to think of weird permutations — like flying to Tokyo
via Frankfurt from the US (a perfectly enjoyable route, just a little longer).