Thanks all for your help and suggestions.

Kakjapan, when did you see availability on CO? I looked yesterday and the online availability looked just like NW, with only 8/31 having "perksaver" economy available. Also, I did notice the availability in February, like you said, but at that point did not know that I would be going (it's a ticket for a companion to travel with me to a meeting).

Themicah, is there any way to check KE availability without signing up for their program? I went to their website but a login was required.

I will keep looking, and will try to call to see if anything else is out there.