What role does the vector line play in a Full Data Block?

The vector line in a Full Data Block is essential as it illustrates the aircraft's intended flight path. This visual representation helps air traffic controllers understand the aircraft's direction and trajectory, enabling them to manage airspace efficiently and maintain safe distances between aircraft. By observing the vector line, controllers can anticipate changes in an aircraft's position, facilitating better coordination and communication with pilots.

The other options, while relevant to flight operations, do not accurately describe the primary function of the vector line. For instance, average fuel consumption is not depicted by the vector line, nor does it display altitude changes or indicate the proximity of aircraft to an airport. Understanding the vector line's role is crucial for effective air traffic management.