NASA has inked a deal with Lockheed Martin to develop a supersonic “X-plane” that could break the sound barrier without a sonic boom, officials said Tuesday.

The $247.5 million contract allows for the design, building and testing of a plane that would make its first test flight in 2021, NASA said.

The experimental plane “will cruise at 55,000 feet (16,764 meters) at a speed of about 940 mph (1,513 kph) and create a sound about as loud as a car door closing, 75 Perceived Level decibel (PLdB), instead of a sonic boom,” the US space agency said in a statement.

As early as mid-2022, NASA plans to fly the X-plane over certain, as yet to be determined, US cities to collect data and gather community responses.

The goal is to enable quieter supersonic flight and create “new commercial cargo and passenger markets in faster-than-sound air travel,” NASA said.

Last month, US President Donald Trump signed a federal budget that fully funds the project, saying the new aircraft “would open a new market for US companies to build faster commercial airliners, creating jobs and cutting cross-country flight times in half.”

But passenger seats are not part of the project Lockheed Martin is working on, at least not yet.

First, the company must show it is possible to fly a quiet supersonic aircraft. Then, the rules of the Federal Aviation Administration would have to be changed in order to lift the current ban on civil supersonic flights over land.

“This X-plane is a critical step closer to that exciting future,” Jaiwon Shin, associate administrator of NASA’s Aeronautics Research Mission Directorate, told a news conference.

Other companies in the process of building supersonic passenger jets for flight in the coming years include Virgin Galactic and Spike Aerospace.