The Boeing 2707 was the first American supersonic airliner project. Being the most advanced of all supersonic airliners created at that time (Concorde, Tu-144) the plane was planned to have seating for 250 to 300 passengers and cruise speeds of approximately Mach number 3.
But the Boeing 2707 was too difficult to implement and was not created.
The project has been closed. Airplanes never flew.
Source: YouTube