Imitation, people say, is the sincerest form of flattery. If that's the case, perhaps Raytheon (NYSE:RTN) should send a thank-you note to General Dynamics (NYSE:GD). General D can, in turn, forward its sincere apologies to Northrop Grumman (NYSE:NOC) for the implied diss.

What in heaven's name are you talking about?
I'm talking about General D's press release yesterday, announcing the successful test of its Counter Man-Portable Airspace Protection System (CMAPS). Designed in response to Homeland Security's call for systems to protect airliners from shoulder-launched surface-to-air missiles (SAMs), General Dynamics' system follows Raytheon's lead in taking a "zone defense" approach to the problem.

As we described as far back as 2005, there are basically two theories on how best to protect airliners from SAM-toting "bad guys in the bushes." Raytheon and General Dynamics think the most cost-effective approach is to set up a perimeter around a site. If a SAM is launched within the perimeter, Raytheon's system will detect the launch and zap the SAM with microwaves.

Man-on-man defense
In contrast to Raytheon's "Vigilant Eagle" and General D's CMAPS, Northrop (and also Britain's BAE Systems) believe in "man-on-man" coverage -- equipping individual aircraft with individual anti-missile systems. Northrop calls its detachable anti-missile pods "Guardian." BAE's analog is dubbed the "JetEye."

The investing angle
Depending on whom you ask, all four major systems have been tested and proven effective. BAE has paired with American Airlines (NYSE:AMR) to test the JetEye's effectiveness in defending Boeing (NYSE:BA) 767s. Northrop spent over a year testing its Guardian pods aboard FedEx (NYSE:FDX) aircraft.

Which system ultimately wins may therefore hinge on cost and convenience. Costwise, Raytheon argues (and General D would agree) that it's cheaper to protect an airfield than the thousands of individual aircraft flying to-and-from it. Specifically, Raytheon claims Vigilant Eagle can protect 84% of America's airports for 20 years at a total cost of $2.6 billion for equipment, installation, and maintenance. Contrasted with a price tag of $41 billion to slap pods on 84% of the planes in U.S. airspace, zone defense seems a no-brainer (unless you're traveling on the other 16%).

General D's ace in the hole
Maybe General D can match Raytheon's price. Maybe not. But even if it can't, CMAPS appears to hold two trump cards. First, it is "portable ... can be rapidly deployed to any airfield... [and] can successfully protect airspace ... infrastructure and ships." Second, it's been tested against unmanned aerial vehicles, and proven capable of shooting these down as well.

Which suggests General D may be imitating Raytheon in two ways. Sounds to me like CMAPS could evolve into competition for Raytheon's Patriot missile batteries. So maybe Raytheon should be sending the General two thank-you notes for the compliments... but I rather think it won't.

More on the people trying to keep safe distance between you and SAM: