&quot;global demand has outstripped supply since Delta started assembling a large and growing fleet in 2012, taking advantage of favorable rental terms and a drop in jet-kerosene prices that makes older planes attractive.<p>“They’re kind of the market-maker,” said Robert Agnew, president and chief executive officer of aviation consultant Morten Beyer &amp; Agnew Inc. “If Delta weren’t there, the airplane might be struggling.”&quot;<p>That&#x27;s the core of the story. It could have been some other model instead. It&#x27;d be interesting to know what the circumstances were behind Delta picking the 717.