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 what NASA Administrator Charlie Bolden described as an “annoying boom” at a news conference Monday. Because of this, supersonic flight is generally 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 likely be appealing to travelers.

“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 association 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.

Most notable, the Concorde made its final flight in October 2003 after being a commercial flop. The plane — which traveled at about 1,500 mph — could cross the Atlantic Ocean in 3½ hours. Yet a roundtrip ticket between the United States and Europe cost over $9,000, and the jet was also alarmingly loud.

Read more on NASA and space: