Jet route is defined for flight operations at which altitude range?

• A. From surface to 20,000 feet
• B. From 10,000 feet to FL 290
• C. From 18,000 feet MSL up to and including FL 450
• D. From FL 600 upward

Answer: (C)

Jet routes represent the high‑altitude enroute system designed for efficient, high-speed IFR flight. They are defined to operate in a specific altitude band that starts at 18,000 feet above mean sea level and goes up to and includes flight level 450 (45,000 feet). The lower limit of 18,000 feet marks the transition from the lower-altitude Victor airways to high-altitude routing, while the upper limit of FL450 keeps jet routes within the standard high‑altitude network. The other options describe airspace or airway ranges that belong to different parts of the enroute structure (lower Victor airways, or altitudes outside the jet routing system). So the correct range is from 18,000 feet MSL up to FL450.