Is there COTS hardware and software for cutting-edge fighter jets? Even Google and Apple create custom OS's for smartphones; I doubt QNX would be a great choice

Is there COTS hardware and software for cutting-edge fighter jets? Even Google and Apple create custom OS's for smartphones; I doubt QNX would be a great choice for a plane. Also, performance is extremely important for this application. If the plane is a little slow, a little too easy to track, the computer a little slow, then the pilots die, the people they are defending are bombed and killed, the battle is lost, and maybe the war too. It's not a place to compromise performance to save money and use COTS, even if it was a available.