Air France (www.airfrance.us) is offering some great fares this fall from its hubs in the U.S. The best seems to be the one between New York and Istanbul for $630 round trip, but some other fares to European destinations are also good.
For instance, Chicago to Prague goes for $982, New York to Paris for $978. You must book two weeks ahead, stay for at least 10 days, and book by September 12.
Don't ask me why it is cheaper to fly to Istanbul than to Paris, since Istanbul is about three hours longer in flying time. It all has to do with competition, or lack of it, I suppose, or perhaps just the popularity of certain destinations.
In any case, the Istanbul fare is quite tempting, and fall is a better time to visit the city on the Bosporus than summer, when the weather can be unpleasantly hot.