JetBlue Profit Down 71 Percent  NEW YORK (Reuters) - Low-cost carrier JetBlue Airways Corp.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=JBLU.O target=/stocks/quickinfo/fullquote"&gt;JBLU.O&lt;/A&gt; on Thursday said third-quarter earnings fell 71  percent as it struggled with skyrocketing fuel prices and tough  competition.