D-21: Lockheed’s Top Secret Mach 3 Drone That Spied on China

The D-21 drone was one of the most mind-blowing top-secret projects of the Cold War – and even today, its speed would be impressive.

The Lockheed Skunk Works has a long and illustrious history of developing some of the top-secret aircraft in the world… From the U-2 to the SR-71 Blackbird, they have been responsible for some of the most advanced aircraft ever conceived. 

But, one project stands out among all others as being shrouded in more secrecy than any other – the D-21.

The Lockheed D-21 drone

The Lockheed D-21
The Lockheed D–21 by U.S. Air Force. Public Domain.

The Lockheed D-21 was a Cold War-era reconnaissance drone designed for the USAF. It was developed in the 1960s as a successor to the U-2 and was first flown in 1964.


The drone was launched from the back of a modified Boeing B-52 bomber, and it could reach speeds of up to Mach 3.2 (three times the speed of sound). But, it could also be launched from an A-12 (a modified Blackbird SR-71).

The D-21 was equipped with cameras and sensors to collect data on enemy targets. However, the drone was retired in 1971 after only seven years of service due to its high cost and limited operational life.

B-52 with two D-21s
B-52 with two D-21s by US Air Force. Public Domain.

Despite its relatively short service life, this incredible drone helped to pave the way for future generations of reconnaissance drones – and it was undoubtedly a breakthrough in the technology of the time.


It gave the US an edge over the Soviet Union

The goal was to develop a high-speed reconnaissance drone that could be launched from an aircraft and returned to base. This would allow the United States to spy on its enemies without risking pilots’ lives.

Especially after the U-2 reconnaissance aircraft was shot down in the Soviet Union.

On May 1, 1960, US Air Force pilot Gary Powers took off from a base in Pakistan on a top-secret mission over the Soviet Union. The mission was designed to gather intelligence on Soviet military installations. However, the mission quickly went awry when Powers was shot down by a surface-to-air missile and taken prisoner by the Soviets.


The incident caused an international uproar – and Powers spent nearly two years in a Soviet prison before being released in a 1962 prisoner exchange.

This incident brought too many inconveniences; therefore, one of the best options was to enter Soviet territory with a drone since, in case it was shot down, there would be no need to negotiate an exchange of prisoners.

The D-21 was a top-secret project

The D-21 drone was eventually developed and became one of the most classified programs in American history.


The drone was so secret that even today, very little is known about it. The few details that emerged suggest that the D-21 was a remarkable feat of engineering. It could fly at incredibly high speeds and altitudes and was able to take clear photographs from long distances.

Unfortunately, the D-21 drone program was eventually scrapped, but it made its mark on history. It served as an important stepping stone in developing unmanned aerial vehicles (UAVs).

Today, UAVs are used extensively for military and civilian purposes, and their popularity is only expected to grow in the years to come – and it would have been impossible without this pioneering drone.


D-21 specs

M-21 & D-21 rearview
M-21 & D–21 rearview by JimCollaborator. Public Domain.

  • Length: 42 feet 10 inches (13.1 meters)
  • Height: 7 feet (2.1 meters)
  • Wingspan: 19 feet (5.8 meters)
  • Max speed: Mach 3.35 (3,600 km/h or 2,300 mph)
  • Service ceiling: 95,000 feet (29,000 meters)
  • Range: 3,500 miles (5,600 kilometers)

The D-21 was the pioneer of drone warfare

This supersonic UAV has been the inspiration for some of the most recent drones – and the next drone projects will indeed have many more capabilities in the future and even surpass the speed achieved by the D-21.

Featured image credit: Lockheed D-21B USAF by CIA. Public Domain.

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