During World War II, fighter planes would come back from battle with bullet holes. The Allies initially sought to strengthen the most commonly damaged parts of the planes to increase combat survivability. A mathematician, Abraham Wald, pointed out that perhaps the reason certain areas of the planes weren’t covered in bullet holes was that planes that were shot in certain critical areas did not return. This insight led to the armor being re-enforced on the parts of returning planes where there were no bullet holes. This wisdom was also beneficially applied to the Skyraider during the Korean War. This shows that the reasons why we are missing certain data may be more meaningful than the available data, itself. In questions of aircraft design, don’t only listen to what the evidence says, listen also to what is not being said.