Yes, two planes have crashed in the air, but not war planes. In 2013, two planes collided mid-air over the Amazon in Brazil, leading to the death of 154 people. The collision was caused by the failure of the air traffic controllers to detect the planes on their radar screens. In 2020, another collision occurred in the United States when a medical transport plane and a single-engine aircraft crashed into each other near South Dakota. Both planes were destroyed and all four people on board were killed.