What do flush rivets help reduce on an aircraft's fuselage?

Flush rivets are designed to sit evenly with the surface of the aircraft's fuselage, which helps to significantly reduce aerodynamic drag. By providing a smoother surface, flush rivets minimize turbulence as air flows over the aircraft, allowing for more efficient movement through the air. This increase in aerodynamic efficiency can contribute to better fuel economy and overall performance of the aircraft.

In terms of other considerations, while weight is a factor in aircraft design, flush rivets specifically do not primarily focus on reducing weight compared to standard rivets. Additionally, thrust and lift are forces related to the aircraft's propulsion and wing design, respectively. The primary purpose of the flush rivet is indeed to enhance the aerodynamics by reducing drag, making it the most relevant choice in the context of aircraft fuselage design.