It sounds like a Tom Clancy novel.
American troops are in battle against some evil foreign power.
The enemy is losing, and in an effort to redress the balance, launches a missile packed with chemical agent. As the missile boosts from a hidden launcher, sensors in a modified Boeing 747 pick up the telltale signature of the launch. Immediately, the crew aboard the craft springs to action. Sensors and radars locate the missile, charge up a laser and fire. The missile explodes, American service members lives are spared, and all is well with the world.