How are jet routes typically numbered?

Jet routes are a specialized type of air route designed for high-altitude aircraft and are primarily found in the United States. They are numbered using a specific convention that helps pilots and air traffic controllers quickly understand the direction of the route at a glance.

The convention dictates that odd numbers are assigned to routes that primarily run in a north-south direction, while even numbers are used for routes that generally extend east-west. This systematic approach to numbering enhances clarity and helps in efficient navigation and communication among aircraft traversing these routes.

For instance, a jet route numbered 31 would be oriented north-south, while a route numbered 24 would represent an east-west orientation. This method not only aids in routing but also allows for easier identification and memorization by pilots and controllers.

This numbering system contrasts with other options that do not accurately describe how jet routes are structured, such as using only even numbers, sequencing across states without regard to the geographic orientation, or grouping by arbitrary numbers.