"Oh Danny boy, the pipes, the pipes are calling
From glen to glen, and down the mountain side
The summer's gone, and all the flowers are dying
'Tis you, 'tis you must go and I must bide."

Will the U.S. Air Force be playing this tune in 2015? Can they get U-2 to play it? Thoughts like these spring to mind as we read today's news: An era is ending. The Air Force is retiring the U-2 spy plane. Yesterday, the Air Force confirmed that the U-2 will make its final flight in 2015, at which point the Lockheed Martin (NYSE: LMT) plane will cede its mission to Northrop Grumman's (NYSE: NOC) unmanned Global Hawk UAV.

In many respects, this news mimics the 2008 retirement of Lockheed's F-117 Stealth Fighter. Like the Stealth, the U-2 is an iconic plane -- once-cutting-edge technology, now rendered obsolete by newer, sharper edges. Also like the Stealth, U-2 was never a big money maker for Lockheed. Only 86 of the planes were ever built -- and fewer than 60 Stealths.

In one important respect, though, this week's news is different: It's bad news for Lockheed.

When the Stealth was canceled, it was to make way for even more advanced stealth-fighter jets like the F-22 Raptor and F-35 Lightning II -- both of which Lockheed also makes, and in greater quantities than the original Stealth. So while Lockheed lost an icon with the Stealth, it gained a larger market, and more potential for profit.

Not so with the U-2's retirement. Here, Lockheed loses both its status as America's premier high-altitude spyplane-builder -- and also loses the spyplane market to a competitor. Adding insult to injury, Northrop's Global Hawk is by many accounts inferior to the U-2. Its top altitude of 65,000 feet is about a mile short of how high the U-2 can fly. Global Hawk is not currently capable of carrying the U-2's hi-res Optical Bar Camera. And according to an Air Force spokesman, its sensor system is only "mediocre."

What it means to you
U-2's farewell gives Northrop added incentive to keep improving Global Hawk's performance, and it's working hard on this. But it also opens up opportunities in spy satellites, for companies like DigitalGlobe and GeoEye … and for Boeing (NYSE: BA) … and for Lockheed itself, to plug the gap. High-Altitude, Long-Endurance (HALE) planes from AeroVironment and Boeing will also certainly try to unseat Global Hawk from its new perch.

In short, U-2's farewell is the end of one era and the beginning of a new one -- with new opportunities for investors.

Want to learn more about up-and-coming spy-satellite makers GeoEye and DigitalGlobe? Make it easy on yourself. Add the companies to your Fool Watchlist, and we'll keep you in the loop.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.