Al-Qaeda and those who align with their vision and methods have a fixation with aircraft. They study avionics, use simulators, document the inner workings for propellers and continually share information about flying, miniature drones and gliders as methods for carrying out terrorist acts. The push for online is due to the fact that the US now scrutinizes all Visas for such activity. It is cost effective; it is now in Arabic having been translated; and since the courses have been simplified so they are not as engineering focused yet still effective.”]
Source: https://www.csoonline.com/article/2136417/joseph-stack–small-aircraft-and-al-qa-eda.html