The engineers can come up with the software and hardware that can cope with any conceivable situation however they can not come up with a design that will not fail. To do so the design of every single component must have a reliability of 1, which means it will never fail. This might be able to be accomplished through redundancy but this is also difficult to achieve.
Present FAA system failure requirements dictate that the system will not fail any more frequently than 1 10e9 or 1 billion hours of fleet operation. Some companies can manipulate the numbers to show that their systems will fail no more frequently than 1 10e17 yet these same aircraft suffer catastrophic failures resulting in loss of life and loss of the airframe.
In almost every civil aircraft design the airframe due to the stringent testing will show a reliability of 1 for the airframe and wings and even these design suffer catastrophic failures.
The engineers can design an aircraft that does not require human intervention and they can prove the reliability on paper showing that nothing will fail but ask them to be on the first test flight and most of them that do not have a death wish will find something else to do.
