For most fearful flyers it is just ignorance of what they think will happen and what will/can happen and lack of being in control. Once I understood more and had it explained my fear dropped by about 90%
For me it has been the complete opposite. The more I fly, the older I get and the more I know about the things that cause plane crashes, the more petrified I have become.
That plane that crashed after taking off from JFK, where the pilot shook the engine off by simply applying his foot on the rudder control for fucks sake.
Heights, Deep Water and in recent years planes all get me. Heights tends to be manageable when my feet are enclosed somehow, but exposed feet = full on attacks. I lasted 10 seconds up the Stratosphere but can get by up the Empire State Building.