When were drones invented—and how did they evolve to become aerial surveillance tools and weapons of war?

The 1895 invention of the radio transmitter and receiver by Italian engineer Guglielmo Marconi sparked an engineering race for uses of the revolutionary new technology—including radio waves to guide aircraft. 

“The dream of pilotless aircraft was already alive in the imagination of numerous engineers by the time the Wright Flyer took off in 1903,” says Roger D. Connor, a curator at National Air and Space Museum in Washington, D.C. “The growth of unpiloted aviation and radio went hand in hand.” 

But radio waves were only the beginning. Below, discover key milestones in the evolution of drone development, the military objectives that drove them, the breakthrough technologies that enabled them—and the turbulence they encountered along the way. 

NEW TECH: Radio remote control

PURPOSE: Attack bombing

FLAWS/CHALLENGES: Unreliable signals

During World War I, British inventor Archibald Low oversaw a top-secret project to produce an “aerial torpedo”—or radio-controlled flying bomb—that would knock out the Germans’ U-boat pens and bring down their Zeppelins. The German Empire considered him such a threat that they twice tried to kill him—once with an exploding cigar, according to Michael J. Boyle, the author of The Drone Age: How Drone Technology Will Change War and Peace.

In March 1917, Low’s dragonfly-like monoplane (dubbed “Aerial Target” to try and fool German spies that it was being used for gunnery target practice) took off for the first time. Compressed air launched the tin-and-wood aircraft, which was briefly maneuverable under radio remote control. 

According to Flight magazine (now FlightGlobal), the first aircraft, launched at a demonstration for the army and navy's top brass, crashed in the mud, prompting one major to complain, “I could have thrown my umbrella further than that.” The second aircraft’s engine shut down during a loop. Low also recalled seeing “a large concourse of brass-hats running for their lives. This mystified me for an instant until, with an appalling crash, the AT landed three yards from where I was sitting… But it had flown, and it had worked.”

Experts attributed the failures to the unreliability of radio signals and the craft’s instability. But the accomplishment eventually led Low to be called the “father of the drone.”

NEW TECH: Telemetry downlinks

PURPOSE: Target practice training

FLAWS/CHALLENGES: Vulnerable to radio interference

The drone found its first practical military use in 1934, when the British navy developed the Queen Bee, a pilotless, radio-controlled de Havilland biplane that could be used as a low-cost flying target for training anti-aircraft gunners.  More than 400 of the buoyant spruce-and-plywood biplanes, which could fly as high as 14,000 feet, were built.

The U.S. Army, meanwhile, turned to World War I pilot, Hollywood star and radar-controlled model aircraft manufacturer Reginald Denny to build drones for military target practice. His Radioplane OQ-2A—launched by a catapult and flown via a control box from the ground—became the first mass-produced U.S. drone. Its successor, the OQ-3, had a maximum speed of 103 mph. More than 9,400 were built.

What made these drones succeed where Low had failed? They were built from cheap, disposable materials like wood, flew realistically and were designed to do one very specific job: to help anti-aircraft gunners learn how to shoot down fast-moving enemy aircraft. Most importantly, they had reliable radio transmitter and receiver technology, which was now being mass produced and miniaturized. In the Queen Bee, for example, new downlinks were able to transmit data like altitude back to the pilot on the ground or in the control plane.  

Radio interference did cause problems for the Queen Bee. In one incident, its receiver picked up a dance band program broadcast by Radio Paris and converted its signal into aerobatic commands “quite unknown” to the Royal Air Force.

NEW TECH: TV guidance

PURPOSE: Attack bombing

FLAWS/CHALLENGES: Mechanical faults, radio interference

The U.S. military still wanted to turn pilotless aircraft into weapons. So, during World War II, they packed worn-out B-17 and B-24 bombers with explosives and turned them into drones with new technology inside them: TV cameras. 

At first, they needed a human pilot for takeoff (who then parachuted out) so the drones could be guided by operators in planes flying nearby who would guide the drones via the rudimentary, blurry TV images. 

But the drones usually fell short of their targets or were shot down by anti-aircraft batteries. One such casualty: Lieutenant Joseph Kennedy Jr., the eldest brother of President John F. Kennedy, who was killed in action while piloting a B-24 drone that prematurely exploded before he and his co-pilot could bail out.

The U.S. Navy also used television to guide twin-engine kamikaze drones called Interstate TDRs, which were launched in the Pacific by ground crews that passed off control to planes in the air. The airborne controller then guided the drone to its target by viewing a screen with TV images from a camera in the drone’s nose.

From July 1944 onward, the Navy launched 50 TDR-1 drones against Japanese targets including anti-aircraft positions, bridges and airfields. Many missed their targets due to radio interference or mechanical faults. But 31 did attack in the face of anti-aircraft fire with no loss of American lives.

NEW TECH: Scientific testing equipment

PURPOSE: Collect atomic blast data

FLAWS/CHALLENGES: Autopilot failure

In July 1946, at the Bikini Atoll in the South Pacific, the United States detonated the first atomic bombs since the destruction of Hiroshima and Nagasaki a year earlier. Minutes later, a fleet of pilotless World War II Grumman Hellcats and Boeing B-17 Flying Fortresses flew directly into the mushroom clouds to test levels of radioactivity, newspapers reported. The full fleet had been "droned" by the addition of a set of radio-controlled instruments; the B-17s had been additionally equipped with television cameras.  

For the first time, bombs and guns were replaced by instruments such as air scoops and collection bags, filter boxes, Geiger counters, radio-controlled cameras and electronic recording instruments. The goal: to sample the radiation in the mushroom cloud and to measure its effect on the plane itself.

The use of pilotless aircraft succeeded. The drones flew through the mushroom cloud, where it was too dangerous for humans to go. The droned Hellcats were launched by catapult from an aircraft carrier for the first time, and only one didn’t return when its controls failed before the test. As for the droned B-17s, “all takeoffs, flight and landings” took place for the first time without pilots and the aircraft completed their missions without significant incidents, according to the official historian of the mission, codenamed Operation Crossroads. 

On August 6, 1946, two of the B-17 drones returning stateside set a record for the longest unmanned flight, with a 2,174-mile journey from Hawaii to California. The New York Times predicted “push-button wars” in the air. 

NEW TECH: Higher-resolution cameras

PURPOSE: Target practice, surveillance, dropping propaganda leaflets and decoys

FLAWS/CHALLENGES: Vulnerable to enemy fighters and anti-aircraft fire. Short range and small payload.

The shark-like Ryan Firebee, one of the first jet-propelled drones, was also one of the first target drones designed for the new missile and jet age. Capable of launching from either the ground or from an airplane in flight, it was used to develop ground-to-air missiles and train pilots flying fighters equipped with missiles. Flown for the first time in 1951, the Firebee I became one of the most successful drones ever, with more than 6,500 built.

Then in 1960, Gary Powers was shot down by a surface-to-air missile while flying his U-2 spy plane over the Soviet Union. Two years later, Rudolf Anderson, Jr. died when his U-2 spy plane was shot down while on a reconnaissance flight over Cuba. Together, these incidents accelerated the effort to mount high-quality cameras onto drones so they could be used for effective surveillance.

“In the late 1950s, there was already a big push to get cameras on board these Firebee drones because the U.S. Army wanted its own reconnaissance capability independent of the Air Force,” says Connor. “But this accelerated after the Cuban Missile Crisis… The vulnerability of the U-2 is a major precipitating event in the growth of the surveillance drone.”

Two years later, the Ryan Lightning Bug jet-powered reconnaissance drone flew for the first time. Ryan drones like these fooled air defenses (one of its innovations was radar-absorbing paint), dropped propaganda leaflets, eavesdropped on enemy communications and acted as decoys, flying some 3,435 sorties. 

On December 14, 1971, a modified Ryan Firebee drone launched the first air-to-ground missile from a remotely piloted aircraft in aviation history, but none was ever used in front line warfare.

NEW TECH: High resolution cameras, more advanced remote control, tethered landing systems, visual monitoring, stealthy reduced noise engines and ability to receive data from sensor on ground

PURPOSE: Surveillance, anti-submarine warfare

FLAWS/CHALLENGES: Reliability

The Vietnam War inspired development of a wide range of drones. The Beech QU-22B, for one, used a remotely operated Beechcraft Bonanza single-engine propeller plane as a relay platform to transmit information from 20,000 low-powered sensors disguised as small trees or bushes that had been dropped onto the Ho Chi Minh trail in Laos. Using a powerful on-board electric generator, the QU-22B collected the sounds and vibrations of North Vietnamese trucks picked up by the sensors in the jungle below, and transmitted them to its base in Thailand. The drone performed its duties well when the equipment worked, but needed a pilot on board for when it didn’t. The loss of several of these aircraft led to the program’s cancellation. 

By contrast, the supersonic, arrow-shaped Lockheed D-21 flew on a pre-programmed path at a maximum speed of over Mach 3, using technology developed for the SR-71 spy plane. Equipped with a high-resolution camera module, it flew several reconnaissance missions to China’s Lop Nor nuclear test site but proved too unreliable. (It undershot the test shot and crashed in China, or overshot and self-destructed over the Soviet Union.) Those that completed their mission dropped their camera module in the wrong place in the Pacific Ocean, or the film was unusable when recovered. 

Then there was the Gyrodyne QH-50 drone helicopter, built to carry torpedoes or a nuclear depth charge for ships too small for a conventional large helicopter. In his book Predator: The Secret Origins of the Drone Revolution, author Richard Whittle writes that the QH-50 was “the most extensive armed UAV program in US history.” 

NEW TECH: Ku-Band satellite antenna, laser designator 

PURPOSE: Long endurance, high-altitude surveillance

FLAWS/CHALLENGES: Reliance on satellite communication, not stealthy, vulnerable to attack by enemy aircraft and missiles

In 1991, during Operation Desert Storm, America and its allies were unable to find Saddam Hussein’s Scud missile launchers in the open desert. According to Connor, the resulting panic eventually led to the development of long-endurance and very high-altitude drones like the Predator to locate them so they could be targeted.

First flown in 1994, the unarmed General Atomics SQ-1 Predator had a bulbous nose, sleek fuselage and long, narrow wings, allowing it to loiter 20,000 feet above targets for 14 hours unnoticed from the ground. 

“It was a huge achievement, but it is the Predator’s advanced electronics rather than airframe which makes that aircraft special,” says Connor. ”Its Ku-Band antenna was the real game-changer.” This allowed the Predator to connect with global satellite communications systems and fiber-optic networks to provide pilots with live video feeds anywhere on Earth with little delay. 

NEW TECH: Hellfire missiles, laser designator, advanced sensors

PURPOSE: Targeting individuals

FLAWS/CHALLENGES:  Reliance on satellite communications, identifying targets, vulnerability to enemy air defenses, missile arming problems

Whittle writes that special forces pilot Scott Swanson was flying the Predator that found America’s most-wanted terrorist—Osama bin Laden—in Afghanistan on September 27, 2000. But being armed only with cameras, and no missiles, he and his colleagues couldn’t take any action against their target, much to their great frustration. 

Senior Air Force leaders had never given up on arming pilotless aircraft,  and the hunt for bin Laden and al-Qaeda had helped accelerate the process. The failure to capitalize on the handful of sightings of the terrorist leader that autumn by the Predator, along with the October 2000 bombing of the USS Cole, upped the urgency. 

As for the right weapon, Air Force brass selected the U.S. Army’s Hellfire (Heliborne-Launched Fire-and-Forget Missile) because it was available immediately. It could be launched from under the wing of a Predator, and it used a laser designator to spotlight targets and guide weapons dropped from other aircraft. The problem was the time it would take to integrate the Hellfire into the Predator systems, and no one knew how the heat and thrust of launching a missile would affect the fragile Predator itself. At its hottest, its plume was 1,050 degrees Fahrenheit. But the Predator’s milliseconds of exposure to the plume means its tail, fuselage and wings will “see” a much lower temperature.

But on February 16, 2001, pilot Carl Hawes made history when he pressed the black launch button on his controller and squeezed the trigger. An unarmed missile flew for three miles and hit its target six inches right of dead center.

One month after 9/11 on October 7, 2001, Swanson was at the controls from Germany when they found bin Laden’s latest hideout, but this time their Predator was armed. He fired two Hellfire missiles to flush him out, but bin Laden escaped and remained in hiding until 2011, when U.S. special forces killed him in Pakistan.

The use of the Predator as an attack drone guided from so far away “was historic,” writes Whittle. “The Hellfire Predator was no longer a concept. A new way of waging war was inaugurated. Remote-control war and remote killing were no longer remote ideas. They were realities.”