By . Ashley Collman . and Mark Prigg . A retired Marine with nearly two decades of aviation experience has stepped forward with a compelling theory about a mysterious plane that was spotted flying over Texas last month. On March 10, photographers Steve Douglass and Dean Muskett took pictures of three puzzling aircraft flying over Amarillo, and posted them online in hopes of identifying the planes. Retired-Marine James Vineyard has submitted one of the more interesting explanations, telling the Houston Chronicle he believes they are SR-72 Blackbirds - a spy plane that can cross the U.S. in less than an hour, unmanned. The triangle over Texas: Two photographers captured this mysterious object flying over Texas last month . Mystery solved? A retired Marine says the plane pictured in Amarillo last month is the SR-72 Blackbird - a plane designed to cross the country in less than an hour . The mystery aircraft  seen over Amarillo on March 10. Three of the craft were spotted flying by . In 1956, British magazines started . getting eyewitness accounts and grainy photos of the Lockheed U-2, then . operating out of RAF Lakenheath on its first spy flights over the Soviet . Union - marking the first sight of a stealth plane that government's . had hoped to keep secret from prying eyes. It provided day and night, very high-altitude (70,000 feet / 21,000 m), all-weather intelligence gathering. Vineyard spent 17 years as a Marine and also worked with a jet squadron in Arizona. He . says the Pentagon may have dispatched the planes to the Indian Ocean to . aide in the search for missing Malaysian Airlines flight 370. But Douglass, who saw the planes himself, doesn't agree. 'The . SR-72 is still in development,' he said Tuesday. 'Plus it's a . high-speed, high-Mach plane. These were going airliner speed. They were . not in a hurry to get anywhere.' The . SR-72 is currently being developed by Lockheed Martin in California, . and according to the company's website they say the plane could be . operational as early as 2030. It . is the predecessor of the SR-71 which broke speed records when it flew . from New York to Lonton in less than two hours in 1976. Lockheed . Martin's Hypersonics program manager Brad Leland wrote that the plane . is designed to 'strike at nearly any location across a continent in less . than an hour.' 'Speed is . the next aviation advancement to counter emerging threats in the next . several decades. The technology would be a game-changer in theater, . similar to how stealth is changing the battlespace today,' Leland said. Another source told the Chronicle that the plane was a B-2, but the two photographers discovered that no B-2s were flying in the country that day . The SR-72 is a successor to the SR-71 which broke speed records when it flew from New York to London in less than two hours in 1976 . Another . reader who wished not to be identified told the Chronicle with . confidence that 'It's a B-2 stealth bomber flying out of Whiteman Air . Force Base in Missouri.' That's . what the photographers thought when they first saw the group of . aircraft, but they say they checked with the base and no B-2s were . flying anywhere in the U.S. that day. Instead, . Douglass believes that the planes are a no type of spy plane - a . stealth transport plane that could sneak troops into a another country . unseen.
A retired Marine says the mysterious plane is an SR-72  - a super-fast spy plane currently in development .
The SR-72 is designed to cross entire continents in less than an hour, unmanned .
Developers at Lockheed Martin say the plane could be operational by 2030 .
The man who photographed the plane doesn't believe it's an SR-72 but rather a stealth transport plane .
By . Ashley Collman . and Mark Prigg . A retired Marine with nearly two decades of aviation experience has stepped forward with a compelling theory about a mysterious plane that was spotted flying over Texas last month. On March 10, photographers Steve Douglass and Dean Muskett took pictures of three puzzling aircraft flying over Amarillo, and posted them online in hopes of identifying the planes. Retired-Marine James Vineyard has submitted one of the more interesting explanations, telling the Houston Chronicle he believes they are SR-72 Blackbirds - a spy plane that can cross the U.S. in less than an hour, unmanned. The triangle over Texas: Two photographers captured this mysterious object flying over Texas last month . Mystery solved? A retired Marine says the plane pictured in Amarillo last month is the SR-72 Blackbird - a plane designed to cross the country in less than an hour . The mystery aircraft  seen over Amarillo on March 10. Three of the craft were spotted flying by . In 1956, British magazines started . getting eyewitness accounts and grainy photos of the Lockheed U-2, then . operating out of RAF Lakenheath on its first spy flights over the Soviet . Union - marking the first sight of a stealth plane that government's . had hoped to keep secret from prying eyes. It provided day and night, very high-altitude (70,000 feet / 21,000 m), all-weather intelligence gathering. Vineyard spent 17 years as a Marine and also worked with a jet squadron in Arizona. He . says the Pentagon may have dispatched the planes to the Indian Ocean to . aide in the search for missing Malaysian Airlines flight 370. But Douglass, who saw the planes himself, doesn't agree. 'The . SR-72 is still in development,' he said Tuesday. 'Plus it's a . high-speed, high-Mach plane. These were going airliner speed. They were . not in a hurry to get anywhere.' The . SR-72 is currently being developed by Lockheed Martin in California, . and according to the company's website they say the plane could be . operational as early as 2030. It . is the predecessor of the SR-71 which broke speed records when it flew . from New York to Lonton in less than two hours in 1976. Lockheed . Martin's Hypersonics program manager Brad Leland wrote that the plane . is designed to 'strike at nearly any location across a continent in less . than an hour.' 'Speed is . the next aviation advancement to counter emerging threats in the next . several decades. The technology would be a game-changer in theater, . similar to how stealth is changing the battlespace today,' Leland said. Another source told the Chronicle that the plane was a B-2, but the two photographers discovered that no B-2s were flying in the country that day . The SR-72 is a successor to the SR-71 which broke speed records when it flew from New York to London in less than two hours in 1976 . Another . reader who wished not to be identified told the Chronicle with . confidence that 'It's a B-2 stealth bomber flying out of Whiteman Air . Force Base in Missouri.' That's . what the photographers thought when they first saw the group of . aircraft, but they say they checked with the base and no B-2s were . flying anywhere in the U.S. that day. Instead, . Douglass believes that the planes are a no type of spy plane - a . stealth transport plane that could sneak troops into a another country . unseen.
retired Marine says the plane pictured in plane designed to cross the country in less than hurry to get anywhere.' The . SR-72 is currently being developed by Lockheed Martin in California, the plane could be . operational as early as in less . than an hour.' 'Speed is . the next of spy plane - a . stealth transport plane that