Final answer:
d) Flight maneuvers and procedures. MTRs are routes used by military aircraft to maintain proficiency in flight maneuvers and procedures.
Step-by-step explanation:
MTRs, or Military Training Routes, are routes used by military aircraft to maintain proficiency in flight maneuvers and procedures. These routes are specifically designed for military purposes and are separate from civilian air traffic management. Military pilots use MTRs to practice various flight maneuvers, such as takeoffs, landings, aerial refueling, and air-to-ground communications.
For example, a military pilot might use an MTR to practice a simulated combat mission or to practice aerial refueling techniques. MTRs provide a controlled environment for military pilots to hone their skills and maintain their proficiency in flight operations.