I woke up to a curious headline on View From the Wing: Have You Ever Been to South Korea?
Turns out if you bought a ticket to or from South Korea on Korean Air Lines or Asiana Airlines between January 1, 2000 and August 1, 2007, you're entitled to come cash and coupons in the settlement process. I spent 3 weeks in South Korea in the summer of 2006, so I went ahead and entered my flight information.
Turns out not only is documentation not required, but flight details aren't even necessary. You just need to specify the number of economy, business, and first class tickets you purchased in each of the eligible years. I entered one economy ticket in 2006, "certified" my response (under penalty of perjury!), and submitted it. It took about 90 seconds.
So if yu traveled to or from South Korea on Korean Air Lines or Asiana Airlines during the eligible period, submit your claim here.