The Airborne Laser Test Bed, officially the YAL-1A, was part of a 15-year, multi-billion dollar research program that ultimately shot down a surface-launched missile.

It has now been retired to the Air Force’s Aerospace Maintenance and Regeneration Group near Tucson, Arizona — more commonly known as “the boneyard:” 

The ALTB, which was a part of the Birk Flight Test Facility at Edwards for more than nine years, was a modified Boeing 747-400 Freighter that housed two solid-state lasers and a megawatt-class Chemical Oxygen Iodine Laser that could use directed energy as a viable technology against ballistic missiles…

“The professional ALTB team built and tested the world’s first airborne megawatt class laser and demonstrated the ability to acquire and track a boosting missile, actively compensate the high energy laser for atmospheric distortions, and place a stabilized laser spot on a boosting missile over hundreds of kilometers,” [Director LtCol Jeff] Warmka said. “In February 2010 we reached the ‘mountain top’ by successfully shooting down a threat-representative ballistic missile – proving the viability of directed energy for missile defense.”

The aircraft and program were mothballed due to budget cuts.