The world’s largest plane is finally being put to use launching hypersonic crafts

California-based startup Stratolaunch successfully completed two hypersonic flights with its reusable autonomous aircraft, the company and US Defense Department announced this week, marking America’s first successful hypersonic flights since 1968, when the legendary rocket-powered X-15 aircraft—still the record-holder for fastest speed by a piloted aircraft—was retired.

What does hypersonic mean? Hypersonic vehicles are highly maneuverable craft capable of flying at least 5x the speed of sound (~3,800 MPH, or fast enough to circumvent the entire Earth in ~6.5 hours). Their combination of speed and agility make them much more difficult to track and intercept than traditional ballistic missiles.

One fast plane piggyback ride

Talon-A, Stratolaunch’s autonomous hypersonic plane that measures a little smaller than a school bus, is kind of like The Beatles—it gets by with a little help from its friend.

• Stratolaunch, founded in 2011 by now-deceased Microsoft cofounder Paul Allen, initially built the world’s largest plane, Roc (wingspan: 385 feet), with the intention of using it to launch satellites into space.
• The company has since pivoted, and now uses Roc to launch Talon-A midair and as a test platform for other hypersonic activity.

Big picture: The tests are part of the Pentagon’s Multi-Service Advanced Capability Hypersonic Test Bed program (MACH-TB), announced in 2022 in a bid to close the technological gap with China, which US officials acknowledge has become the world's leader in hypersonic missile development.