"There are those that see JSF as the last manned fighter. I'm one that's inclined to believe that."
-- Adm. Michael Mullen, former chairman of the U.S. Joint Chiefs of Staff

It's been a good six months or so since we last checked in on the wonderful world of flying robots that kill. Plenty of time for developments to crop up. So, what have our future robot overlords been up to lately?

Well, taking over the Air Force, for one thing. If you should happen to find yourself wandering the highways and byways of Pakistan sometime in the next few months, and you notice an erratic bomb or rocket falling from the sky, chances are a robot launched it. According to a new report out of the Congressional Research Service (CRS), fully 31% of the "airplanes" currently being flown by the U.S. Air Force are actually "drone" aircraft. This, by the way, is a six-fold increase in six years. As recently as 2005, only one plane in 20 was a drone.

Name that drone
From an investor's perspective, that's a pretty respectable-looking growth rate -- but the transformation of the Pentagon's air forces (both within the actual Air Force and in the other services as well) has actually been even more dramatic. From 2002 to 2010, the Pentagon reports that its inventory of drones increased 40 times in size. At last report, the U.S. military possessed some 10,700 piloted airplanes of various shapes and sizes, and nearly 7,500 drones.

But who is it, exactly, that makes all these flying robots? If we're not supposed to invest in defense companies anymore, seeing as Lockheed Martin (NYSE: LMT) has already invented "the last manned fighter" and all, who are we to invest in?

Actually, there are quite a few companies to choose from. For example, we know that United Technologies (NYSE: UTX) is hard at work transforming part of its helicopter fleet from piloted to "optionally piloted" status as it tests the feasibility of converting the venerable Black Hawk into a robotic helo. Among two-winged drones, the CRS lists three key players:

  • General Atomics, which makes the Predator, Reaper, Grey Eagle, and soon the jet-powered Avenger
  • Northrop Grumman (NYSE: NOC), prime contractor for the Hunter and Global Hawk
  • Textron (NYSE: TXT), manufacturer of the Shadow (that's right. That Shadow.)

Of these three, only Northrop and Textron are currently public companies that you can invest in. But the possibilities are actually wider than that. Lockheed, for example, makes a drone called the RQ-170 Sentinel -- the so-called "Beast of Kandahar." You may have heard of this one, which flew into a bit of a PR fiasco last year when one of its drones made an unscheduled and highly embarrassing landing in Iran.

Boeing (NYSE: BA), too, has a place in the UAV space. A few years back, its ScanEagle played a critical role in the freeing of Maersk Alabama Captain Richard Phillips off the coast of Somalia. It's also developing a new robotic helo called the A160 Hummingbird to conduct resupply missions for the Army.

They've got momentum!
That said, for the time being at least it seems likely that the incumbents in the UAV industry are doing everything right to maintain pole position in this race. This year, General Atomics and Northrop combined will collect roughly 80% of the dollars the U.S. military spends on medium-sized and large UAVs. And going forward, the Pentagon's increased focus on operations in the Asia-Pacific region suggests that companies focusing their efforts on large UAVs with long flight endurance -- such as General Atomics makes -- should garner a disproportionately large share of the Pentagon's UAV budget. Contractors who demonstrate proficiency in carrier- and other warship-launched UAVs -- Northrop's forte -- could do even better.

As a result, choosing the company best-placed to profit, and holding the most promise as an investment, becomes a really easy choice. We can't buy privately held General Atomics. We can buy publicly traded Northrop Grumman. And with fears over budget cuts having pushed the shares down below nine times earnings, where they now pay a 3.4% dividend ... maybe we should.

What other stocks are poised to profit from governmental backing? Find out, in the Fool's new free report -- Too Small to Fail: Two Small Caps the Government Won't Let Go Broke.