A few years ago, Chairman of the Joint Chiefs of Staff Admiral Mike Mullen assured Lockheed Martin (NYSE:LMT) investors that their company's F-35 Lightning II fighter jet was the only game in town -- probably the "last manned fighter jet" the U.S. would ever build. Fast-forward a few years, and the Pentagon's under new management. Air Combat Command Mike Hostage now says that the U.S. needs a whole "family of systems" for its Air Force, and could begin building a new, sixth-generation fighter jet in as little as 18 years.

What does this mean for Lockheed and for the F-35's engine builder, United Technologies (NYSE:UTX)? What opportunities does it open up for rival plane builders such as Boeing (NYSE:BA) and Northrop Grumman (NYSE:NOC)? Listen in, as Fool contributor Rich Smith explains.

Fool contributor Rich Smith has no positions in the stocks mentioned above. The Motley Fool owns shares of Lockheed Martin and Northrop Grumman. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.