skimthetrees

It's complicated, but yeah, you cannot under any circumstances extend the AS booking calendar beyond what dates the calendar will show. The problem is JL availability usually does not show for the last few days of the AS calendar. This trick is to work around that AS block on JL availability in the last few days of their calendar. If you do a straight one-way search, Alaska blocks JL availability for the last few days of its schedule (4-6 days?). You can force those dates to show by using the reverse round-trip trick.

I was playing around to see how you found the one-way award near the end of the AS calendar. Unless you were doing some weird search method the only thing I came up with is that if another airline has an award available in the block period (last 6 days or so of the AS calendar) then AS will show all flights on that day including JL flights that would normally not be shown in that block window. Do you recall if their were other airline flights showing available on 6/15 when you searched one-way?

The only way to book beyond the AS calendar window is to book with another program like BA, CX, QF, that has a longer booking window.