This thread is from last spring (original post from March, last response from May). A lot has changed since then (an understatement) and most points made in response to this particular thread are no longer relevant.
There are not many direct flights from the US to Prague, since it's a relatively small market and mostly for leisure (as opposed to business) travelers; most often you will need to connect someplace in Europe, and those few nonstops that do exist often only run "seasonally" (that is, only during the busy summer travel season when demand is high enough for the airlines to justify them). Seasonal routes like that come and go, and it's hard to predict next year's availability with great certainty.
Tip: If you have a question about a specific flight or routing, it's best to post a new thread with your specific question, rather than resuscitate an old thread from months ago like this one, which will just cause confusion as others will try to reply to a discussion that's well past its "best by" date.