You might try ITT Travel. They're a military and family travel agency. Usually they have lower rates than some of the other sites. However, the lower cost comes with lots of connections, long layovers and less than ideal schedules. I've had pretty good luck with Travelocity. Check the site frequently especially on Tuesdays and Wednesdays; sometimes you can hit it just right. We were looking to fly our son back from Okinawa for the holidays and it was looking like the fare was going to be a little over $1500. I checked the fare twice within 15 minutes and I got a rate of a little over $1000 on different carriers. So it pays to be persistent. The rate was about $70 lower than that on ITT travel but it included a 20 hour layover. Not worth the savings in my opinion.
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Also would advise considering flying into Milwaukee...may be a cheaper flight with a lot less chaos than O'Hare