Somewhere above your head, right now, there is a small robotic spaceplane that the United States has been flying for more than fifteen years — and the government will not tell you what it does. It looks like a Space Shuttle that shrank in the wash. It launches on a rocket, disappears into orbit for a year or two or three, and then glides home to a runway on autopilot.

It is called the X-37B, and it is the closest thing we have to the winged military spaceplane the Cold War kept trying, and failing, to build. Except this one is real, it flies, and it is very, very quiet about its business.

The Space Force’s pet mystery

The X-37B is built by Boeing and operated by the U.S. Space Force. There are two of them, and between them they have racked up more than 4,200 days in orbit since the first flight in 2010. Each is about 29 feet long — roughly a quarter the length of the old Space Shuttle — with a payload bay about the size of a pickup truck bed. There is no crew. It flies itself, all the way from orbit to the moment its wheels touch the runway.

A SpaceX rocket launches the X-37B, which later glides back to a pinpoint autonomous runway landing.

Years in orbit, lips sealed

What makes the X-37B genuinely strange is how long it stays up. Its sixth mission lasted nearly 909 days — almost two and a half years in orbit before it came home. Across all its flights, the little spaceplane has spent well over a decade’s worth of days circling the Earth.

Officially, it tests reusable spacecraft technologies and carries experiments for the government. Unofficially, its knack for changing its orbit and vanishing from where trackers expect it has made it a favourite Cold-War-style headache for America’s rivals — a point a former Air Force secretary once made with unusual candour.

The X-37B returns from one of its record-length orbital missions.

So what is it actually doing up there?

The honest answer is that most of it is classified — which is exactly why the X-37B attracts so much breathless speculation. It has been accused of being a spy platform, a satellite inspector, even a space bomber, a claim the Pentagon flatly rejects. What the Space Force will confirm is more prosaic and, arguably, more interesting: it is a flying test bench.

Its seventh mission practised “aerobraking” — skimming the top of the atmosphere to change orbit while sipping fuel. Its eighth, launched in August 2025, is testing high-speed laser communications and the highest-performing quantum navigation sensor ever flown in space — a way to navigate without GPS.

The Dyna-Soar dream, finally flying

Strip away the secrecy and the X-37B is the answer to a question first asked more than sixty years ago. The Air Force tried to build a reusable, winged military spaceplane in the 1960s and cancelled it: that was the X-20 Dyna-Soar. It tried again with a crewed spy station and cancelled that too: the Manned Orbiting Laboratory. The Soviets chased the same idea with their little folding-wing Spiral.

All of them failed. The X-37B is what those programmes were reaching for — a small, reusable spaceplane that launches on a rocket, manoeuvres in orbit, lingers for months on end, and glides home to fly again. It just took half a century, and a robot instead of a pilot, to finally make it work.

A Falcon Heavy launches the X-37B on one of its secretive orbital missions.

Sources: U.S. Space Force; Boeing; NASA; Spaceflight Now; The War Zone; Aspen Security Forum (2019).