Eyes in the Sky: Top Secret Spy Planes

The Predator earned a reputation as a spy plane when it first appeared in the skies over Bosnia to support NATO operations. But more recently, this unmanned aerial vehicle was outfitted with Hellfire missiles, and that armament has figured in many lethal attacks on targets in Iraq and Afghanistan.

The first such attack to gain notoriety came when a Predator destroyed a civilian vehicle in Yemen carrying suspected terrorists in 2002. A favorite weapon of the CIA since 2001, the Predator can send back imagery to a 30 foot long command and control trailer thousands of miles - and a continent away - remaining in place for hours as it tracks a target.

Over the past couple of years, the number of Predator attacks has climbed sharply, and the drone is now routinely described in press reports as a key component of U.S. counter terrorism strategy.

The MQ-4 Global Hawk unmanned aerial vehicle from Northrop Grumman is effective in clouds, sand storms - whatever atmospheric impediments Mother Nature throw its way. The craft can survey up to 40,000 square miles in a single day.

The craft is also finding use in non-military arenas. It has become the workhorse for NOAA's DARPA has announced that it is is developing an unmanned aircraft which would be able to remain aloft for over five years without needing to land. We'll see.

If you like triangles and trapezoids, you'll love the F-117 Nighthawk, shown here soaring over The Sierra Nevada Mountain Range.

Any history of surveillance aircraft must include a major chapter on the F-117. Developed at Lockheed Martin's famous "skunk works," it was the first plane to use stealth technology to evade enemy radar. It wasn't 100% - a F-117 got shot down by ground fire while on a mission against former Yugoslavia in 1999.

Still, the airplane is hard to see on a radar screen, thanks in part to the exterior materials which bounce off or absorb radar signals.

The Air Force retired the fleet in 2008.

Boeing's new flying wing, the Phantom Ray, is said to be a testbed for unspecified "advanced technologies." When it offered the public its first peak at the craft last year, the company described a myriad of possible missions the aircraft might undertake; these ranged from surveillance to "strike." Boeing separately - and vaguely - made reference to a potential mission for the plane as a "hunter/killer."

Affectionately known as the Dragon Lady, the Lockheed U-2 has been around in various incarnations since 1955. This undated photo from the Lockheed Martin corporation shows the U-2 reconnaissance aircraft. It's an oldie but a goodie. With its long wingspan, the U-2 can travel effortlessly at up to 70,000 feet while it photographs ground positions. The exterior of the plane has remained the same since its original flight but the U-2 has been upgraded with more sophisticated reconnaissance equipment over the decades.

Last April, the U.S. Air Force launched the X-37B, an unmanned military spacecraft from Cape Canaveral, Fla. on a 270-day mission that has largely remained shrouded in mystery to this day. What we do know is that the craft is roughly a quarter of the size of the space shuttle. In 1999, the Pentagon took control of the program from NASA, where the X-37B began. But what exactly is the nature and cost of the X-37B? The Air Force is not saying.

Fodder for a bar room debate: Did the Aurora ever really exist? For the record, the U.S. military has consistently denied rumors that it built this supposed mid-1980s United States reconnaissance aircraft. The stories date back to 1990 when Aviation Week & Space Technology reported that it found the name "Aurora" in the 1985 budget for something described as "black aircraft production." It was described in some reports to be able to reach speeds of Mach 8, thus enabling it to reach any point on Earth within three hours. Indeed, over the years, there have been frequent sighting claims but, so far, no bird in the hand, so to speak. Make that "high altitude" bird in the hand.

The twin-engine turboprop MC-12W is one of the U.S. Air Force's newest surveillance craft and will augment the fleet of Predator and Reaper UAVs now in use. But unlike the drones, the plane is flown by human pilots. That human element affords a ground units more and complementary options when the battlefield changes. One pilot interviewed by Wired magazine in Afghanistan put it this way: "I consider knowledge a weapon."

The military describes the craft as "a complete collection, processing, analysis and dissemination system." It includes an electro-optical infrared sensor with a a laser illuminator and designator to provide intelligence assistance to ground forces. It also includes advanced data links and satellite communications equipment.

Upgraded versions of the RC-12X Guardrail are slated for delivery to the army in the second quarter. The modernization program will extend the life of the craft to at least 2025 and also equip it with more advanced signals intelligence capability. The craft was designed to work in tandem with ground units, offering up precision geo-location data and other intelligence information to infantry.