80 Years After the X-1, Why NASA Still Builds X-Planes

NASA's X-59 is flying over US towns this year to test whether a stretched, anteater-shaped nose can turn a sonic boom into what its program manager compares to a car door closing across the street, according to BBC News (25 September 2026). The aircraft is the newest entry in a line of experimental "X-planes" that stretches back 80 years to the Bell X-1, the plane that first broke the sound barrier in 1947, BBC News reported.

How Does The X-59 Reduce Sonic Booms?

A jet crossing the sound barrier produces a shockwave that reaches the ground as a boom. That effect kept Concorde restricted to overwater routes and shut it out of many US flight paths, according to BBC News. NASA's answer with the X-59 is an elongated nose designed to flatten the shockwave before it reaches the ground. Peter Coen, who has worked at NASA for 43 years and manages the X-plane program, told BBC News the goal is to get the boom down to a level people find tolerable "on a regular basis." He estimated the aircraft will sound "like a car door being closed across the street" when it crosses Mach 1 — roughly 660 mph at airline cruising altitude, per BBC News.

"We want to figure out what level of boom is acceptable to people on a regular basis," Coen told BBC News.

The X-59 first flew in 2025, according to BBC News, and NASA is pairing its test flights with community surveys asking residents how the softened boom compares with ordinary background noise.

How Fast Did Earlier X-Planes Go?

The X-1's shape came from a simple data point: NASA engineers knew a .50-caliber bullet traveled faster than sound, so the aircraft was built like a bullet with wings, BBC News reported. Test pilot Chuck Yeager flew it past Mach 1 in 1947.

Two decades later, the X-15 — a cylinder with small wings dropped from a B-52 bomber — reached 6.7 times the speed of sound, or 4,520 mph, and touched the edge of space, according to BBC News. That flight data fed directly into the heat-resistant materials later used on the Space Shuttle, per the same report.

Why Build A Piloted Jet Instead Of A Drone?

BBC News reports that NASA considered an uncrewed version of the X-59 before settling on a piloted design. Two factors drove that choice, according to the outlet. First, certifying an autonomous jet to fly fast over populated US towns would have added its own cost and regulatory complexity — removing the pilot did not automatically make the program cheaper. Second, the X-59 needed to be built at a scale close to an airliner to generate a boom signature relevant to future supersonic passenger travel, a size requirement that exists independent of whether a human sits in the cockpit.

Coen's broader philosophy, as described to BBC News, is to keep each X-plane focused on a single, narrow objective: "Our approach is to pick small goals we aim to prove with flight data and we construct an airframe for that one task." He added that expanding the goals of any single aircraft is what drives up its cost — the opposite of what a cheap, mass-produced drone is designed to do.

What Parts Did The X-59 Borrow From Other Aircraft?

The X-59 is assembled from components already in production, according to BBC News: the cockpit and ejector seat come from the T-38 training jet, the landing gear from the F-16 fighter, and the engine from the F-18. Because the cockpit sits far back on the fuselage, the pilot has no direct forward view and instead relies on a camera feeding a screen, processed in real time by onboard computers. Lockheed Martin built the aircraft for NASA, BBC News reported.

Data Box: X-Plane Program By The Numbers

• 1947 — Year the Bell X-1 became the first aircraft to break the sound barrier, per BBC News.
• 6.7 times the speed of sound (4,520 mph) — Top speed of the X-15, reached about 20 years after the X-1, according to BBC News.
• 660 mph — Approximate speed of Mach 1 at airline cruising altitude, cited by NASA's Peter Coen in BBC News.
• 43 years — Coen's tenure at NASA, per BBC News.
• 2025 — Year the X-59 first flew, according to BBC News.

What Happens Next For The X-59?

NASA's community surveys are ongoing as the X-59 continues flights over selected US towns, BBC News reported. The data collected on how residents perceive the softened boom will inform whether regulators eventually permit supersonic flight over land — the market Concorde was barred from decades ago. No timeline for a regulatory decision was given in the BBC News report.

For more on how NASA's X-plane program compares with today's uncrewed aircraft push, read the original BBC News report.

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