Update (March 14, 2013):  $399 is gone, but there’s a pretty good fare on Air France “Super Spring Sale.”  Purchase before March 26 — as low as $667 New York >< Istanbul round-trip.  Departures through April 30.  I found March 30 >< April 10 @ $691.  Most fares are just under $710. Update (February 20, 2013):  We’ve…