The record-shattering mission of the U.S. Air Force's robotic X-37B space plane is finally over. 
 
 After circling Earth for an unprecedented 718 days, the X-37B touched down Sunday (May 7) at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida — the first landing at the SLF since the final space shuttle mission came back to Earth in July 2011. The landing occurred at 7:47 a.m. EDT (1147 GMT). 
 
 "Today marks an incredibly exciting day for the 45th Space Wing as we continue to break barriers," Air Force Brig. Gen. Wayne Monteith, the 45th SW commander, said in a statement. "Our team has been preparing for this event for several years, and I am extremely proud to see our hard work and dedication culminate in today's safe and successful landing of the X-37B." [The Mysterious X-37B Space Plane: 6 Surprising Facts] 
 
 The U.S. Air Force's X-37B Orbital Test Vehicle mission 4 (OTV-4) is seen after landing at the Shuttle Landing Facility of NASA's Kennedy Space Center in Cape Canaveral, Florida on May 7, 2017. The unpiloted space plane spent a record 718 days in space during its classified mission. Credit: U.S. Air Force 
 
 The just-ended mission, known as OTV-4 (Orbital Test Vehicle-4), was the fourth for the X-37B program. All four launched from Florida's Cape Canaveral Air Force Station, and the first three landed at Vandenberg Air Force Base in California. But Air Force officials have said they want to consolidate X-37B launch and touchdown operations on Florida's Space Coast, so today's landing might be the first of many at the SLF. 
 
 "The hard work of the X-37B OTV team and the 45th Space Wing successfully demonstrated the flexibility and resolve necessary to continue the nation's advancement in space," Randy Walden, the director of the Air Force Rapid Capabilities Office, said in the same statement. "The ability to land, refurbish, and launch from the same location further enhances the OTV's ability to rapidly integrate and qualify new space technologies." 
 
 The Air Force is known to possess two X-37B space plane vehicles, both of which were built by Boeing. The 29-foot-long (8.8 meters) X-37B looks like NASA's now-retired space shuttle orbiter, only much smaller; indeed, two X-37Bs could fit inside a space shuttle's cavernous payload bay. 
 
 The X-37B launches vertically and comes back to Earth horizontally for a runway landing, as the space shuttle did. 
 
 Most of the X-37B's payloads and activities are classified, leading to some speculation that the space plane could be a weapon of some sort, perhaps a disabler of enemy satellites. But Air Force officials have always strongly refuted that notion, stressing that the vehicle is simply testing technologies on orbit. [The X-37B's Fourth Mystery Mission in Photos] 
 
 Technicians in protective gear work on the U.S. Air Force's X-37B Orbital Test Vehicle after its successful landing at NASA's Kennedy Space Center Shuttle Landing Facility in Cape Canaveral, Florida on May 7, 2017. NASA's massive Vehicle Assembly Building is visible in the distance at top right. Credit: U.S. Air Force 
 
 
 
 Space weapon tests: It's a secret project to make war in space. 
 
 Space surveillance: It's the world's best spysat platform. 
 
 Space tech tests: The U.S. military is pushing the robotic spaceflight frontier. 
 
 Peaceful uses in space: The X-37B is quiet because it's a robot and doesn't talk. 
 
 
 
 "Technologies being tested in the program include advanced guidance, navigation and control; thermal-protection systems; avionics; high-temperature structures and seals; conformal, reusable insulation, lightweight electromechanical flight systems; and autonomous orbital flight, re-entry and landing," Capt. AnnMarie Annicelli, an Air Force spokeswoman, told Space.com via email in March. 
 
 "Also, the Air Force Research Laboratory (AFRL), Space and Missile Systems Center (SMC), and the Air Force Rapid Capabilities Office (AFRCO) are investigating an experimental propulsion system," she said. 
 
 Outside experts generally agree with the Air Force's claims, saying it's unlikely that the X-37B is doing anything aggressive or nefarious on orbit. Some observers have suggested that, in addition to the roles cited by Annicelli, the vehicle may be testing sensors for the National Reconnaissance Office, which operates the United States' fleet of spy satellites. 
 
 Each X-37B flight has been longer than the last. OTV-1 lifted off on April 22, 2010, and spent 224 days in space; OTV-2 launched on March 5, 2011, and orbited Earth for 468 days; and OTV-3 began on Dec. 11, 2012, and lasted 674 days. (OTV-4 lifted off on May 20, 2015.) 
 
 Though OTV-4 set an X-37B program record, the mission fell far short of the overall mark for longest spaceflight mission. Some Earth-observing satellites have operated for decades, and NASA's twin Voyager 1 and Voyager 2 probes are still sending data home, nearly 40 years after their 1977 launches. 
 
 Editor's note: This story was updated Monday, May 8 to include the landing time for X-37B contributed by reporter Irene Klotz. 
 
 Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com. ||||| Although the Air Force has disclosed some of the payloads that have flown to orbit on the X-37B, most of the space plane's onboard gear is classified, as are the details of its orbital activities. This secrecy has led to some speculation that the vehicle is some sort of space weapon, perhaps one designed to take out or capture satellites. However, the Air Force has always denied this notion, insisting that the X-37B is just testing out technologies for future spacecraft, and carrying various experiments up to space and back. Some of these technologies being tested may be sensors and other equipment for future spy satellites, outside experts have said. ||||| Mission: The X-37B Orbital Test Vehicle, or OTV, is an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force. The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth. 
 
 
 
 Features: 
 
 The X-37B Orbital Test Vehicle is the newest and most advanced re-entry spacecraft. Based on NASA’s X-37 design, the unmanned OTV is designed for vertical launch to low Earth orbit altitudes where it can perform long duration space technology experimentation and testing. Upon command from the ground, the OTV autonomously re-enters the atmosphere, descends, and lands horizontally on a runway. The X-37B is the first vehicle since NASA’s Shuttle Orbiter with the ability to return experiments to Earth for further inspection and analysis, but with an on-orbit time of 270 days or greater, the X-37B can stay in space for much longer. 
 
 
 
 Technologies being tested in the program include advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, advanced materials and autonomous orbital flight, reentry and landing. 
 
 
 
 Background: 
 
 The Air Force Rapid Capabilities Office is leading the Department of Defense’s Orbital Test Vehicle initiative, by direction of the Under Secretary of Defense for Acquisition, Technology and Logistics and the Secretary of the Air Force. The Air Force OTV effort uses extensive contractor and government investments in the X-37 program by the Air Force, NASA and the Defense Advanced Research Projects Agency to continue full-scale development and on-orbit testing of a long-duration, reusable space vehicle. 
 
 
 
 NASA’s original X-37 program began in 1999 and ran until September 2004 when NASA transferred the program to DARPA. NASA envisioned building two vehicles, an Approach and Landing Test Vehicle, or ALTV, and an Orbital Vehicle. The ALTV validated flight dynamics and extended the flight envelope beyond the low speed/low altitude tests conducted by NASA from 1998 through 2001 on the X-40A, a sub-scale version of the X-37 developed by Air Force Research Labs. DARPA completed the ALTV portion of the X-37 program in September 2006 by successfully executing a series of captive carry and free flight tests. NASA’s X-37 Orbital Vehicle was never built, but its design was the starting point for the Air Force’s X-37B Orbital Test Vehicle program. 
 
 
 
 The Air Force has successfully flown four X-37B missions, OTV-1 through OTV-4, beginning with its first launch on April 22, 2010 from Cape Canaveral Air Force Station, Fla. OTV-1 through OTV-3 all landed successfully at Vandenberg AFB, Calif., and the most recent mission, OTV-4, successfully landed at Kennedy Space Center, Fla. on May 7, 2017, after 718 days in orbit. The first four OTV missions have spent a total of 2,085 days on orbit, successfully checking out the X-37B’s reusable flight, reentry and landing technologies as well as operating experiments to benefit the national space community. 
 
 
 
 General Characteristics: 
 
 Primary Mission: Experimental test vehicle 
 
 Prime Contractor: Boeing 
 
 Height: 9 feet, 6 inches (2.9 meters) 
 
 Length: 29 feet, 3 inches (8.9 meters) 
 
 Wingspan: 14 feet, 11 inches (4.5 meters) 
 
 Launch Weight: 11,000 pounds (4,990 kilograms) 
 
 Power: Gallium Arsenide Solar Cells with lithium-Ion batteries 
 
 Launch Vehicle: United Launch Alliance Atlas V (501) 
 
 NEWS INFO Date Taken: 05.07.2017 Date Posted: 05.07.2017 08:02 Story ID: 232877 Location: WASHINGTON, DC, US Web Views: 3,265 Downloads: 4 Podcast Hits: 0 PUBLIC DOMAIN This work, X-37B Orbital Test Vehicle Fact Sheet, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright. ||||| CAPE CANAVERAL, Fla. (Reuters) - The U.S. military’s experimental X-37B space plane landed on Sunday at NASA’s Kennedy Space Center in Florida, completing a classified mission that lasted nearly two years, the Air Force said. 
 
 The unmanned X-37B, which resembles a miniature space shuttle, touched down at 7:47 a.m. EDT (1147 GMT) on a runway formerly used for landings of the now-mothballed space shuttles, the Air Force said in an email. 
 
 
 
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 The Boeing-built space plane blasted off in May 2015 from nearby Cape Canaveral Air Force Station aboard an Atlas 5 rocket built by United Launch Alliance, a partnership between Lockheed Martin Corp (LMT.N) and Boeing Co (BA.N). 
 
 The X-37B, one of two in the Air Force fleet, conducted unspecified experiments for more than 700 days while in orbit. It was the fourth and lengthiest mission so far for the secretive program, managed by the Air Force Rapid Capabilities Office. 
 
 The orbiters “perform risk reduction, experimentation and concept-of-operations development for reusable space vehicle technologies,” the Air Force has said without providing details. The cost of the program is also classified. 
 
 The Secure World Foundation, a nonprofit group promoting the peaceful exploration of space, says the secrecy surrounding the X-37B suggests the presence of intelligence-related hardware being tested or evaluated aboard the craft. 
 
 The vehicles are 29 feet (9 meters) long and have a wingspan of 15 feet, making them about one quarter of the size of the National Aeronautics and Space Administration’s now-retired space shuttles. 
 
 Slideshow (4 Images) 
 
 The X-37B, also known as Orbital Test Vehicle, or OTV, first flew in April 2010 and returned after eight months. A second mission launched in March 2011 and lasted 15 months, while a third took flight in December 2012 and returned after 22 months. 
 
 Sunday’s landing was the X-37B’s first in Florida. The three previous landings took place at Vandenberg Air Force Base in California. The Air Force relocated the program in 2014, taking over two of NASA’s former shuttle-processing hangars. 
 
 The Air Force intends to launch the fifth X-37B mission from Cape Canaveral Air Force Station, located just south of the Kennedy Space Center, later this year.
– The Air Force owns two X-37B space planes, and one of them is finally back on the ground after a nearly 2-year-long secret mission. While the what is unknown, the how long is clear: 718 days in orbit, reports Space.com, with the unmanned plane landing Sunday morning at NASA's Kennedy Space Center in Florida—and flying into the record books. It was the Air Force's fourth such mission since April 2010 and the longest to date. A fifth is planned for 2017, reports Reuters. There's plenty of speculation about what the 29-foot-long plane, which looks like a mini-space shuttle, is up to up there. Reuters cites one group's belief that the secrecy indicates intelligence-related hardware tests are being conducted. An Air Force fact sheet offers up this much: "The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth." One cool fact: Though its mission is classified, its location isn't, thanks to what Space.com refers to as "keen-eyed amateur astronomers." The site offers a satellite tracker when missions are active, and notes the X-37B "usually looks like a star of middling brightness moving across the sky."