Lockheed engineers are <a href="http://www.cnn.com/2013/11/05/tech/innovation/new-spy-plane/index.html">developing a hypersonic aircraft</a> that will go twice the speed of the SR-71 Blackbird, which goes three times the speed of sound. That aircraft, seen in this photo illustration, is called the SR-72 or "Son of Blackbird." Take a look through the gallery to see other stealth and spy planes.
Stealth and spy planes —
Lockheed engineers are developing a hypersonic aircraft that will go twice the speed of the SR-71 Blackbird, which goes three times the speed of sound. That aircraft, seen in this photo illustration, is called the SR-72 or "Son of Blackbird." Take a look through the gallery to see other stealth and spy planes.
Lockheed martin
An SR-71B Blackbird flies over snow-capped mountains in 1995.
Stealth and spy planes —
An SR-71B Blackbird flies over snow-capped mountains in 1995.
NASA/Hulton Archive/getty images
An A-12 reconnaissance aircraft, the predecessor to the SR-71, is seen on display at the Intrepid Sea, Air and Space Museum in New York City in August 2010.
Stealth and spy planes —
An A-12 reconnaissance aircraft, the predecessor to the SR-71, is seen on display at the Intrepid Sea, Air and Space Museum in New York City in August 2010.
Lance Cheung/U.S. Air Force)
The EP-3E Aries II aircraft is a reconnaissance aircraft that uses electronic surveillance equipment for its primary mission. One of them was in the news in April 2001 when it collided with a Chinese jet.
Stealth and spy planes —
The EP-3E Aries II aircraft is a reconnaissance aircraft that uses electronic surveillance equipment for its primary mission. One of them was in the news in April 2001 when it collided with a Chinese jet.
US NAVY/AFP/Getty Images
The F-117 Nighthawk is one of the most famous and successful stealth aircraft. It was the first plane to be completely designed around the aspect of stealth, and its development was kept a secret in the early 1980s.
Stealth and spy planes —
The F-117 Nighthawk is one of the most famous and successful stealth aircraft. It was the first plane to be completely designed around the aspect of stealth, and its development was kept a secret in the early 1980s.
AFP/Getty Images
Lockheed's "Have Blue" prototype was the predecessor of the famed Nighthawk.
Stealth and spy planes —
Lockheed's "Have Blue" prototype was the predecessor of the famed Nighthawk.
49th Wing History Office
The Northrop YB-49 was not considered stealth aircraft, but its "strategic bomber" design set the foundation for the B-2 Spirit, a future stealth bomber.
Stealth and spy planes —
The Northrop YB-49 was not considered stealth aircraft, but its "strategic bomber" design set the foundation for the B-2 Spirit, a future stealth bomber.
U.S. Air Force
A B-2 Spirit soars over the Pacific Ocean in May 2006.
Stealth and spy planes —
A B-2 Spirit soars over the Pacific Ocean in May 2006.
Staff Sgt. Bennie J. Davis III/U.S. Air Force
The Lockheed YF-12 flies a test mission near Edwards Air Force Base in California.
Stealth and spy planes —
The Lockheed YF-12 flies a test mission near Edwards Air Force Base in California.
U.S. Air Force
The YF-22A fighter, first produced in 1990, used stealth technology and became the first fighter-type aircraft to achieve sustained supersonic flight without employing afterburner.
Eyes in the sky, seen and unseen —
The YF-22A fighter, first produced in 1990, used stealth technology and became the first fighter-type aircraft to achieve sustained supersonic flight without employing afterburner.
Lockhead/Department Of Defense/Time Life Pictures/Getty Images
The F-22 Raptor interceptor, which uses stealth technology, completed its first successful flight in 1997.
Stealth and spy planes —
The F-22 Raptor interceptor, which uses stealth technology, completed its first successful flight in 1997.
PAUL CROCK/AFP/Getty Images
The MQ-1 Predator is an unmanned aircraft, or drone, that has conducted reconnaissance and surveillance missions.
Stealth and spy planes —
The MQ-1 Predator is an unmanned aircraft, or drone, that has conducted reconnaissance and surveillance missions.
Tech. Sgt. Sabrina Johnson/U.S. Air Force
In the 1950s, aircraft like these RB-47s conducted surveillance missions over the Soviet Union and other "denied areas," but they became increasingly vulnerable to enemy defenses.
Stealth and spy planes —
In the 1950s, aircraft like these RB-47s conducted surveillance missions over the Soviet Union and other "denied areas," but they became increasingly vulnerable to enemy defenses.
National Recon Office
The Convair RB-36D was the jet-augumented version of the U.S. Air Force's intercontinental strategic bomber. The bomb bay was fitted with 14 cameras, and the No. 2 bay was used to carry 100-pound photo flash bombs for nighttime aerial photography.
Stealth and spy planes —
The Convair RB-36D was the jet-augumented version of the U.S. Air Force's intercontinental strategic bomber. The bomb bay was fitted with 14 cameras, and the No. 2 bay was used to carry 100-pound photo flash bombs for nighttime aerial photography.
U.S. Air Force
The U-2 high flying spy plane, developed by Lockheed, was considered stealthy because of its ability to fly at extremely high altitudes. But the Soviet Union's defense radar was still able to detect the aircraft.
Stealth and spy planes —
The U-2 high flying spy plane, developed by Lockheed, was considered stealthy because of its ability to fly at extremely high altitudes. But the Soviet Union's defense radar was still able to detect the aircraft.
Central Press/Getty Images
CIA pilots stand in pressure suits in front of a U-2 plane. The pilots needed the pressure suits for the extremely high altitudes.
Stealth and spy planes —
CIA pilots stand in pressure suits in front of a U-2 plane. The pilots needed the pressure suits for the extremely high altitudes.
National Recon Office