Also, look at flights going through SFO. I live in the DC area and travel to Korea two to three times a year. If you avoid the May-August months, you can probably get a flight on United for about $1000-1300.
The other way around that is to book his flights separately; if you do that, you can usually get a ICN-SFO r/t flight on Singapore for $800-1000. Then get him a r/t from SFO to IAD nonstop.
I'll always ride an Asian airline over a US-based airline because the seats, inflight entertainment, and food are almost always better...