For many years the systems are being designed to be immune to the failures. This means that when a system or a sub-system fails still the system/subsystem must be able to function to the maximum extent. The best example for this is Auto pilot and manual piloting of the Aircraft. Generally the modern Aircrafts fly in auto pilot mode over long distances in a pre designated path using onboard mission computers. When the auto pilot system malfunctions it will warn the pilots and switches over to manual mode. This will allow the aircraft to fly safely and land in nearest airfield in spite of the failure of a critical system.
