The French were among the innovators militarizing the air as early as 1794, when a lighter than air observation balloon tracked the movements of Austrian troops before and during the Battle of Fleurus. France was an early customer of the Wright Brothers, and soon began developing and building its own aircraft, with innovations kept secret from competing militaries. Italy followed, and by 1911 deployed reconnaissance and bomber aircraft against their enemy during the Italo-Turk War. Reconnaissance and photo-reconnaissance roles for aircraft were recognized by all armies, and they strove to develop airplanes superior to those of potential enemies.
During World War I, the United States Army developed a flying bomb, a self-guided “aerial torpedo” developed by a consortium which included several names forever linked to aviation. These included Elmer Sperry, Orville Wright, Henry Ford, and Charles Kettering. The aircraft was developed under such strict secrecy that few in the Army’s highest offices knew of its existence. Though it never flew in combat, it remains the forefather of the cruise missiles and unmanned aerial vehicles in use today. Here are 10 “secret” airplanes developed for military use from around the world.
10. Morane-Saulnier Type L
During the early phases of World War One, wing-mounted machine guns were impossible, since the vibrations of the gun firing would shake the airplane apart. There was also the problem of cocking the guns, and providing them with ammunition. Firing forward from an airplane which used a tractor propeller was impossible. Several observation planes had rearward firing weapons, and pilots occasionally engaged each other using sidearms, but the true fighter plane did not yet exist. Then in April, 1915, a French Morane-Saulnier Type L, a monoplane, shot down three German observation planes with the pilot – Roland Garros – firing a machine gun through his own wooden propeller without damaging it. The French had a new secret weapon, and the opportunity to rule the skies over Europe.
It didn’t stay a secret very long. Garros was forced to land behind German lines following his third victory in April, and was captured by German troops before he had time to destroy the system. The secret was an interrupter gear, which worked sporadically, and angled metal wedges attached to the propeller, which deflected bullets which hit them. Germany had already been developing its own interrupter gear and its designer, Anthony Fokker, declined to augment it with the wedges, believing them to be too dangerous for the pilot, who could easily be hit by a deflected bullet. By July Fokker’s system of synchronizing the gun and propeller was deployed, and the Germans ruled the skies over the Western Front from then until the British and French countered in early 1916.
9. The Amerikabomber
To strike at the United States mainland by air from Germany required a bomber capable of flying 7,200 miles, carrying a bomb load sufficient to make the trip worthwhile. The German Luftwaffe began developing potential designs for such a bomber in 1938. In the early years of World War II, the Azores, ruled by Portugal, became a fueling stop for German U-boats. Hitler and Goering envisioned using land bases on the islands as launching points for bombing missions against American cities. Several German manufacturers submitted plans for bombers to participate in the Amerikabomber project, including Junkers, Focke-Wulf, Heinkel, and Messerschmitt.
In the end, only two such bombers were built, the Messerschmitt Me 264 and Junkers Ju 390. By the time prototypes were available for testing the Portuguese were leasing bases in the Azores to the Allies, for air cover to protect the convoys to Great Britain. Eventually the Ju 390 became the preferred aircraft to serve as the Amerikabomber. According to records and eyewitnesses, only one ever flew. Years after the war claims surfaced that it once flew from Bordeaux to New York and returned undetected, though the overwhelming evidence discounts the story. Hitler certainly wanted to bomb New York and presumably Washington, though he never had an airplane capable of completing the mission.
8. The U-2
The Lockheed U-2 Dragon Lady developed as a result of the need to closely monitor events within the Soviet Union and its allies during the height of the Red Scare of the 1950s. It was designed and developed in the tightest possible secrecy, despite requiring the participation of experts in aerial photography, new engine technology, new fuels to operate those engines, and the hundreds of technicians and engineers needed to build the aircraft. The prototypes were tested in secrecy at Area 51, though it had not yet been designated with that name, now linked in the minds of some with conspiracy theories, little green men, and Unidentified Flying Objects.
Operated by the CIA and US Air Force (eventually the US Navy as well), the use of the U-2 as a spy plane remained secret from the American public. It was described as a weather monitoring aircraft supporting the National Advisory Committee for Aeronautics, which later became part of NASA. When the Soviets shot down a U-2 flown by Francis Gary Powers in 1960 the true nature of the aircraft was revealed. It was U-2 photo-reconnaissance over Cuba which revealed the existence of nuclear capable missiles there, and led to the Cuban Missile Crisis in October 1962. Another U-2 was lost during overflights of Cuba that month. Officially, the CIA stopped their participation in the U-2 program in 1974, but the US Air Force and other agencies continued to use the aircraft in 2020, well over 60 years after it first flew in secret at Area 51.
7. Lockheed A-12
In the 1960s the CIA attempted and failed to reduce the radar cross-section of the U-2. At the same time, Soviet radars improved steadily, and the high-flying U-2 became increasingly susceptible to detection. The result was a CIA led program known as Project Oxcart. The program resulted in Lockheed’s development of the A-12, a twin engine reconnaissance aircraft constructed mainly of titanium. As with the U-2, the project was conducted in total secrecy, and the developmental aircraft were tested and modified mainly at Area 51. When one test aircraft crashed in October 1963, the pilot ejected safely and was returned to the base after reporting the crash at a local police station.
The CIA announced the crashed airplane had been an F-105 Thunderchief, and that it had been carrying nuclear weapons, the latter to dissuade locals from visiting the site. It also paid eyewitnesses to the crash and immediate aftermath to remain silent about what they saw. The A-12 flew nearly 2,000 test flights (18 were built) though it never conducted flights over the Soviet Union, as was originally intended. It did conduct some flights over Southeast Asia, conducting reconnaissance of North Vietnamese surface-to-air missile (SAM) sites, flying in excess of 80,000 feet of altitude. Its last mission came in February 1968, when it overflew the USS Pueblo and charted North Korean missile sites.
6. Lockheed YF-12
During the development of the A-12, the United States Air Force expressed interest in a modified version, expanded to two seats and capable of carrying air-to-air missiles. Aircraft would be capable of flying higher and faster than any other interceptor in the world, with speeds in excess of Mach 3. The seventh, eighth, and ninth models of the A-12 were adapted to the Air Force specifications and delivered to Area 51 for testing and evaluation, with the first flight taking place in August 1963. As with the A-12, the program was shrouded in secrecy for the initial flights. That ended in February 1964, when President Lyndon Johnson announced the existence of the airplane to the world.
Johnson’s motives were to distract interest from the A-12 test flights for the CIA, implying the spy plane was a prototype for the Air Force’s new superfighter. The YF-12 set speed and altitude records during evaluation at Edwards Air Force Base, and the Air Force eventually placed an order for more than 90 variants known as the F-12B, but the increasing budgetary pressures of the Vietnam War forced Secretary of Defense Robert McNamara to deny the funding to pay for them. In January 1968, the F-12 program was officially canceled, with the fighter having never entered production.
5. F-117 Nighthawk
In the 1970s a Lockheed analyst read a paper written, ironically enough, by a Soviet mathematician, which presented a new description of how radar cross-section is determined. The paper, and others along the same lines, presented the basis for the development of aircraft nearly undetectable to radar. It led to the development and eventual production of the F-117 Nighthawk, which remained a closely guarded secret for over a decade. When it did become known to the press and public in 1988 it was quickly labeled the “stealth fighter,” though it was not a fighter aircraft. The Nighthawk was developed as a ground support and attack aircraft.
The first operational aircraft was delivered to Area 51 in 1981, and eventually a total of 64 were built by Lockheed. For much of its early development it was a black program, with the initial prototypes funded by DARPA, and it continued to be hidden within the Air Force’s budgets for years. The aircrafts themselves were based at Tonopah Test Range in Nevada, while the pilots and their families were based at Nellis Air Force Base, over 200 miles away. The pilots were shuttled by air to fly the F-117 until 1989, and their families, and others, were told they flew A-7 Corsairs until the aircraft was officially revealed in 1988. The Nighthawks took part in several combat operations before being officially retired in 2008, though there are reports of the aircraft observed in flight as recently as 2019.
4. Lockheed SR-71
In 1962, using funds from a black program, the United States Air Force ordered a variant of the CIA’s A-12, which was eventually designated the SR-71. The aircraft was essentially a continuation of the YF-12 program, with some modifications including the installation of photo-reconnaissance cameras and radar countermeasures. The aircraft’s main defenses were its speed, which could reach a sustained Mach 3.2, and the altitude at which it operated. The aircraft also carried electronic intelligence (ELINT) sensors, side-looking airborne radar (SLAR) and various other sensors and data collecting systems throughout its career. The two-man crew wore specially designed pressurized suits and full helmets, appearing similar to astronauts.
Officially, the US government never operated SR-71s over the Soviet Union and later Russian Confederation (though they made the same claim over the U-2 flights until they were caught). They did fly over North Vietnam during the Vietnam War, and several had SAMS shot at them by the North Vietnamese, but no SR-71 was ever lost due to enemy action. The SR-71, which became known as the Blackbird due to its dark paint scheme, was partially retired by the Air Force in 1988, primarily due to Congressional budget cuts. Some aircraft were reactivated for a time, but in 1998 it was fully retired by the Air Force. NASA continued to operate the SR-71 until the following year. Today the once Top Secret airplane can be viewed in several museums.
3. Boeing X 37B
The Boeing X37B is an unmanned reusable orbiting vehicle, which launches via a booster rocket and returns to earth to land on a runway. Originally developed under contract with NASA, the program was absorbed by the Air Force in 2004. The orbiter is essentially a robotic vehicle capable of long, extended missions in space, which have all been top secret as of this writing, as is the contents of the payload section which it carries. In May 2020 it launched into space on its sixth mission. As of August, it remained in orbit.
The dearth of official information on what the spaceplane, as some call it, actually does in space led to the belief espoused by some that it is a weapon, or a space weapons test bed, or both. Others claim it is used to spy on satellites of other nations. Officially, the Air Force claims the orbiter is used to conduct long term experiments in space and return the results to earth for further analysis and evaluation. Boeing announced the development of a larger version of the orbiter capable of carrying a pressurized capsule in the payload section in 2011. The variant would be capable of carrying up to six astronauts in space. The most recent mission of the X 37B was officially the first under the auspices of the recently created United States Space Force.
2. MQ-1 Predator Drone
Although well known to the general public today, largely due to its performance in combat in several actions, the Predator was initially developed in secret by the CIA and the US Air Force as an unmanned aerial reconnaissance vehicle. The Predator’s early flights were conducted in secrecy in the Mojave Desert in the mid-1990s. During the period between January 1994 and June 1996 the Predator was evaluated in the Advanced Concept Technology Demonstration Phase. The USAF, US Navy, US Army, and the US Marine Corps all participated, training system operators and technicians.
Originally the drones were intended as reconnaissance vehicles, and when the first were acquired by the Department of Defense they were given the military designation of RQ-1 Predator. R signified reconnaissance, and Q designated the aircraft as unmanned. After the design was modified to carry weaponry it became known as the MQ-1 Predator. Its extensive use in Afghanistan, Iraq, Iran, and in the earlier Balkans conflicts earned it global fame, though for some notoriety may be considered a better term. In 2018 the USAF retired the MQ-1 Predator, though it remains in use with some civilian applications.
Although rumors of a replacement for the retired SR-71 preceded it for several years, Lockheed Martin revealed a proposed unmanned aerial vehicle in 2013, to fly at speeds up to Mach 6 (nearly twice the speed of the SR-71). Since then, other than an announcement that the USAF had an “interest” in the project, there has been little hard information. Some speculate a demonstration vehicle would be ready to fly by 2023. Others have speculated it is already flying in secret, presumably at the same test grounds as its predecessors. Lockheed Martin announced a flying prototype capable of firing hypersonic missiles would be available for evaluation in 2025.
The US Department of Defense has claimed that despite successful testing of various components, a hypersonic missile is still years away, with 2023 the earliest potential date of possessing a vehicle for testing. Yet rumors of test platforms already flying persist, including reports of the demonstrator being seen landing at Lockheed Martin’s test facilities in Palmdale, California, escort by US Air Force T-38 trainers, in 2017. Since all of the airplanes listed here were in development and testing long before their existence was acknowledged to the public, the speculation may have basis in fact. It won’t be known until the veil of secrecy is lifted.