What do the red numbers on an airway indicate?

The correct choice relates to the purpose of the red numbers on airways, which indicate speed restrictions. In aviation, airways are like highways in the sky, and just as highways may have speed limits for safety and efficiency, airways may also impose specific speed restrictions for aircraft traveling along those routes. These red numbers serve as essential guidance to pilots, informing them of the maximum or minimum speed they should maintain while flying through certain segments of an airway. This information helps ensure safe separation between aircraft and contributes to the overall flow of air traffic.

Understanding speed restrictions is crucial for pilots to maintain proper spacing and avoid potential conflicts with other aircraft, especially in congested air traffic areas. Other options may reflect various air traffic management concepts, such as altitude restrictions, flight path changes, or navigation aids, but they do not pertain to the specific function of red numbers on airways.