Q and jet routes serve aircraft operating at what altitude range?

Jet routes and Q routes are specifically designated for high-altitude flight operations, which include airspace used primarily by jets. These routes are designed to facilitate the efficient movement of aircraft and are part of the National Airspace System (NAS) in the United States. They connect major airports and provide a structured pathway for aircraft flying at higher altitudes.

The altitude range for jet routes starts at 18,000 feet Mean Sea Level (MSL) and extends up to and including Flight Level 450 (FL450), which is approximately 45,000 feet MSL. This high-altitude range is critical for ensuring that commercial jets, which typically operate at higher cruising altitudes, have clear and efficient paths while minimizing conflicting traffic.

Other altitude ranges mentioned in the other choices do not pertain to Q and jet routes, as those altitudes are either below standard jet operating levels or do not encompass the designated high-altitude airspace that these routes are intended for. Thus, the correct answer highlights the operational altitude range for jet routes, ensuring safe and efficient air travel at higher flight levels.