Weaponized lasers will likely be a feature on the battlefield of the future. Even though only one of the weapons was ever built and the program has been discontinued, the YAL Airborne Laser Testbed was an important proof of concept.
The American weapon, which was first tested successfully in 2007, was housed inside a converted 747 aircraft, which had the largest laser turret ever built installed on the plane's nose. The laser was built to intercept tactical ballistic missiles midway through their flight path, and in a 2010 test, the YAL succeeded in shooting down a test target.
The military decided the YAL was impractical — in order to intercept a missile, the aircraft would have to already be in the air, while the weapon itself was expensive to fabricate, operate, and maintain. Still, it demonstrated that enormous, high-powered lasers could destroy large and fast-moving objects, and do so in mid-air.
If lasers ever become a feature of aerial combat, it will be because of the precedent of the YAL.