How are integral fuel tanks on transport aircraft primarily formed?

Integral fuel tanks on transport aircraft are primarily formed by the aircraft structure itself. This means that the fuel tank is integrated into the airframe components, such as the wings or fuselage, rather than being a separate, removable unit. The construction of integral fuel tanks utilizes the existing structure of the aircraft, which allows for efficient use of space and weight. By incorporating the fuel tank directly within the structural components, the design enhances overall aerodynamics and reduces the number of potential fuel leaks, as there are fewer seams and joints compared to modular or external tank designs.

This approach provides a strong, lightweight solution that also contributes to the overall structural integrity of the aircraft while optimizing fuel storage capacity. The seamless integration of the tanks minimizes the chances of contamination and simplifies maintenance, making it the preferred method in modern aircraft design.