The Airborne Laser, envisioned as a fleet of converted Boeing 747s that would fire laser beams to destroy enemy missiles soon after launch, before they could release decoys.
It turned out that the lasers could not be fired over sufficient distances, so the planes would have to fly within or near an enemy’s borders continuously. That would leave the 747s all but defenseless against antiaircraft missiles. The program was canceled in 2012, after a decade of testing.
The problem would have gone smoothly if they had used tried technology. For example, instead of 747s they should have gone with DC-10s, as they have successfully been converted in the past even for interstellar travel. And you could always go with sharks of course... No missile deployment stands any chance against a sharknado... with lasers...