For technology to be adopted it has to be relevant and cost effective. Man has been able to go to the moon since 1969 but since 1972 it has not been cost effective and its relevance has diminished. It is still possible however. Autonomous passenger aircraft don't meet the relevance and cost effective criteria. Airline travel is still the safest form of travel despite its complexity. The technology that is currently in aircraft meets the cost effective and relevance criteria because 2 pilots are still present. Once they are taken out then the cost of the technology is going to skyrocket because of the certification and testing of the concept. Its not just the technology required to get the plane off the ground and back on in a safe manner. What about the integration with ATC, integration with airports, handling of diversions, handling of emergencies. Its not just about flying from A to B. Yes the technology exists but what is the relevance and is it more cost effective? Technology does not = zero accidents.