What was once the largest solar power plant of its type in the world appears headed for closure just 11 years after opening.

What was once the world's largest solar power plant of its type appears headed for closure just 11 years after opening, under pressure from cheaper green energy sources. Meanwhile, environmentalists continue to blame the Mojave Desert plant for killing thousands of birds and tortoises.

About 35,000 feet (10,670 meters) over the Mojave Desert, northwest of Los Angeles, Boom Supersonic's XB-1 became the first privately funded airplane to break the sound barrier during a test flight on Tuesday.

Colorado-based Boom Supersonic plans to build the Overture airliner, which it says will carry as many as 80 passengers while moving at about twice the speed of today’s subsonic airliners.

The countdown has begun for the XB-1’s “historic” first supersonic test flight that should break the sound barrier, according to Boom Supersonic.