Reversion to lower levels of automation disables built in protections, possibly leading to unsafe conditions if pilots continue to rely on them. Automation controls are designed so that they are difficult to access and activate quickly and accurately, or easy to activate inadvertently.
Automation is too complex to understand and use effectively.
Automation is not thoroughly tested before use and it may not perform correctly under certain conditions. Automation designers have difficulty in making good decisions about allocating functions to humans or to automation, leading to poor function allocation decisions. Automatic flight control systems use a different strategy of control than the pilot, leading to the pilot's loss of situation awareness and pilot errors.