Sitting cramped in coach on a long flight can be unbearable. And NASA feels your pain. The agency is funding early efforts to build a plane so fast it could whisk you to any city on the planet in six hours or less.

NASA is giving Lockheed Martin about $20 million in a preliminary design contract to demonstrate a “low boom” aircraft.

When planes exceed the speed of sound — 767.269 mph — they generate an “annoying boom,” NASA Administrator Charlie Bolden said at a news conference Monday. Because of this, supersonic flight is prohibited over the United States.

NASA envisions a plane that emits a quieter sonic boom, more like a subtle thump. If supersonic flights were quiet enough to be allowed widely, the appeal of shorter flight times would probably draw travelers and make these planes a viable technology.

“We will be able to achieve the full potential of revolutionary technology and designs that lift aviation to the next level of flying higher, safer and faster,” said Jaiwon Shin, NASA’s associate administrator for aeronautics research.

There have been other efforts at supersonic flight since the sound barrier was first broken in 1947, but none have taken hold.