The Boeing X Thirty-Seven B, the Space Force's Orbital Test Vehicle That Has Been Flying Autonomous Missions for Fifteen Years, and What an Unmanned Space Plane That Lands on a Runway Tells Us About Where Aviation Is Going

The Boeing X-37B Orbital Test Vehicle has completed six fully autonomous orbital missions since its first flight in April 2010, with the longest lasting 908 days - over two and a half years in orbit. Every phase of these missions, from launch to runway touchdown, is controlled by onboard computers with no human pilot. A seventh mission, launched in December 2023, remains ongoing.

What Is the X-37B?

The X-37B is a reusable, unmanned spacecraft built by Boeing Phantom Works. At 29 feet long with a wingspan of nearly 15 feet and a launch weight of approximately 11,000 pounds, it resembles a miniature Space Shuttle - intentionally. It shares the same delta wing platform, the same ceramic thermal protection tiles on its underside and nose, and carries a small payload bay.

The vehicle launches encapsulated inside a standard payload fairing atop a rocket, operates in orbit for extended periods, then reenters the atmosphere and lands on a runway without crew.

How the Program Developed Across Three Agencies

The X-37B’s origins trace to NASA in the late 1990s, when the agency was investigating small, reusable orbital vehicles capable of autonomous landing. Drawing on lessons from the Space Shuttle, NASA wanted to determine whether a vehicle could manage its own terminal guidance without a crew. Early approach and landing tests took place at Edwards Air Force Base.

In 2004, NASA transferred the program to DARPA, which flew the X-37B as an atmospheric test vehicle. DARPA validated low-speed handling and approach characteristics through full-stop runway landings before the vehicle ever reached orbit - building a flight characteristics database from the ground up.

In 2006, the U.S. Air Force took custody, transitioning the program from technology demonstrator to operational platform.

Six Missions, Six Autonomous Landings

The first mission launched in April 2010 on an Atlas V rocket from Cape Canaveral. It landed 224 days later at Vandenberg Air Force Base in California - autonomously, on a runway, in the middle of the night.

Mission durations increased steadily across each flight:

Mission 1: 224 days
Mission 2: 468 days
Mission 3: 674 days
Mission 4: 717 days
Mission 5: 780 days
Mission 6: 908 days (launched May 2020, landed November 2022)

Mission 7 launched in December 2023 aboard a SpaceX Falcon Heavy and remains in orbit as of this writing.

The Hardest Approach in Aviation

The X-37B faces arguably the most demanding terminal approach problem in all of aviation: a runway landing with no engine, no go-around option, and no pilot.

The reentry sequence begins with a deorbit burn from low Earth orbit at approximately 17,000 mph. The vehicle enters the upper atmosphere through a reentry corridor roughly one to two degrees wide. Enter too steeply and the thermal protection system is overwhelmed. Enter too shallowly and the vehicle skips off the top of the atmosphere - unable to attempt reentry again with no fuel remaining.

Threading that corridor at Mach 25 requires continuous monitoring of altitude, velocity, angle of attack, and aerodynamic forces. Onboard computers make constant corrections through the wing’s elevons, managing energy bleed along a planned trajectory. The mathematical framework is recognizable to any pilot who has run a fuel burn calculation on a long-range operation - the difference is that constraint temperatures on the windward tiles reach approximately 3,000 degrees Fahrenheit.

Once subsonic, the vehicle flies a 20-degree glideslope - roughly seven times steeper than a standard 3-degree ILS approach. The steep angle preserves airspeed and aerodynamic control authority through the entire descent. The flare begins at approximately 2,000 feet above the runway. Touchdown occurs at around 220 knots. The drag chute deploys. The vehicle rolls out. Only then does a human being physically touch it.

Ground controllers at Schriever Space Force Base in Colorado monitor telemetry throughout, but communication latency makes them observers, not pilots in any meaningful sense. The machine is flying itself.

The Thermal Protection System and Its History

The X-37B’s thermal protection system descends directly from Space Shuttle technology, continuously refined over decades. The most vulnerable areas - the nose cap and wing leading edges - use reinforced carbon-carbon composites capable of withstanding temperatures no metal alloy survives. The underside uses ceramic tiles with a silica fiber core: highly effective thermal insulators, but structurally fragile.

Space Shuttle Columbia was lost on February 1, 2003, when foam shed by the external tank during ascent struck the left wing leading edge, damaging tiles and allowing superheated plasma to penetrate the structure on reentry. The X-37B’s design incorporates lessons from that accident directly. The vehicle launches encapsulated inside its payload fairing, protecting the tiles from ascent damage entirely - there is no external tank to shed debris. Six missions have come home intact.

What Is Mission 7 Doing Up There?

The Space Force has not publicly disclosed the specific objectives of any X-37B mission. What is publicly confirmed: the payload bay is approximately the size of a pickup truck bed. Mission 6 carried a solar power demonstration from the Air Force Research Laboratory that successfully converted solar energy to a microwave beam and transmitted it from orbit - a meaningful proof of concept for future energy systems. Previous missions have deployed small experimental satellites, and several have carried Hall-effect ion thrusters, which accelerate ionized gas electrostatically to produce highly fuel-efficient thrust.

The vehicle can adjust its orbital altitude and inclination, changing its ground track to overfly different areas at different times. Combined with a payload bay that can carry classified instruments, the X-37B represents a maneuverable, persistent, autonomous orbital platform capable of operating for over two years continuously. The full details of what the Space Force is doing with that capability are not publicly available.

Why This Matters for Pilots

The X-37B was never designed to make a civilian aviation argument. But aviation technology rarely stays in one lane.

GPS originated as a purely military program. Traffic collision avoidance systems emerged from government and industry research following mid-air disasters stretching from the 1950s through the 1970s. Weather radar, inertial navigation, and terrain awareness technology all have military and space program ancestors that were refined under demanding operational conditions before reaching the civil cockpit. The pattern is consistent across decades.

The X-37B represents fifteen years of operational data on one specific question: can a computer independently manage the most demanding approach profile in aviation, repeatedly, under varying conditions, with no human backup? Across six missions, the answer is yes.

That answer does not automatically translate to certified autonomous operations under FAA oversight. The regulatory and certification pathway for autonomous civil aviation is a separate, enormous challenge. The X-37B’s environment is also simpler in some respects - no traffic conflicts, a cleared and prepared runway, and maximum ground support during setup.

But the capability gap is narrowing from both directions. Reliable Robotics is pursuing autonomous operations in the Cessna Caravan. Airbus has demonstrated fully autonomous approaches on commercial-category aircraft in testing. Current-generation airliner autopilot systems handle full autoland in zero-zero conditions. The X-37B sits at the far edge of that progression - an extreme data point in a field steadily moving toward routine autonomous aviation, with the central question shifting from whether a computer can land an aircraft to under what conditions and with what regulatory framework.

The solar arrays that sustain the X-37B through extended missions also represent fifteen years of development in lightweight, high-efficiency photovoltaics. Those efficiency gains - driven by military and NASA programs - have a documented downstream path into the solar-supplemented hybrid-electric platforms several general aviation startups are building today.

The technologies cross back over. They always have.

Key Takeaways

The Boeing X-37B has flown six fully autonomous orbital missions since 2010, with the longest lasting 908 days; a seventh mission launched in December 2023 is still ongoing.
Every mission ends with an autonomous runway landing on a 20-degree glideslope at approximately 220 knots, with no pilot, no go-around option, and no second chance.
The program passed through NASA, DARPA, and the U.S. Air Force before becoming a Space Force operational asset.
The vehicle’s thermal protection system incorporates direct lessons from the Space Shuttle Columbia loss in 2003; six missions have returned intact.
Fifteen years of autonomous reentry and landing data from this program are feeding the engineering conversations that will define civil autonomous aviation in the 2030s and beyond.

Sources: Spaceflight Now mission reporting; American Institute of Aeronautics and Astronautics technical papers; Air Force Research Laboratory public reporting on the space solar power demonstration from Mission 6.