Final answer:
Frontal thunderstorms are the most dangerous to flying due to severe weather conditions and resulting turbulence.
Step-by-step explanation:
The most dangerous type of thunderstorm for flying is the frontal thunderstorm. Frontal thunderstorms form along a weather front where two air masses with different temperatures and humidity collide. They often have a large area of severe weather, including strong winds, hail, and heavy rain. These conditions can create dangerous turbulence and visibility issues for aircraft.