What does “flying the line” refer to?

“Flying the line” refers to the practice of following established flight routing and procedures during an operation. This term encompasses adhering to the prescribed airways, waypoints, altitudes, and other procedural guidelines set forth in the flight plan and relevant air traffic regulations. By doing so, pilots ensure they maintain safe and efficient navigation, which is fundamental to instrument flight operations.

In this context, the phrase highlights the importance of precision and compliance with aviation regulations, particularly under instrument conditions where visual references may be limited. The adherence to such procedures is critical for maintaining situational awareness, deconflicting with other air traffic, and ensuring safety in congested airspaces.

While preparing the aircraft for takeoff, executing emergency maneuvers, or conducting pre-flight inspections are essential components of flight operations, they do not encapsulate the definition of "flying the line" as it specifically pertains to following the prescribed routes and guidelines once airborne.