A chart symbol resembling a chain link fence refers to which type of routing?

The chart symbol that resembles a chain link fence is used to denote compulsory routing, which is a directive given to pilots that they must follow specific routes during their flight. This is essential for maintaining order and safety in busy airspace, ensuring that all aircraft adhere to designated paths as prescribed by air traffic control. This routing helps in managing the flow of air traffic and minimizing the risk of collisions or unintended deviations from flight paths.

In contrast, substitute routing is not represented by that chart symbol and generally refers to alternative routes that may be used under certain circumstances. Preferred routing indicates routes that are typically favored for efficiency but are not obligatory. Mandatory routing involves strict compliance with specific airways or routes, similar to compulsory routing but may apply under different regulatory contexts. Thus, the chain link fence symbol effectively communicates the requirement pilots have to adhere to a defined routing, which is a critical aspect of air traffic management.