What is the purpose of step-down fixes in a flight plan?

• A. They increase speed only
• B. Step-down fixes require altitude changes at specified fixes to maintain airspace constraints
• C. They have no effect on altitude
• D. They are optional restrictions

Answer: (B)

Step-down fixes define where you must descend to specific altitudes along a route to follow the published vertical profile. They’re used to enforce airspace constraints, obstacle clearance, and proper sequencing with other traffic as you move through en route and approach segments. When you reach a step-down fix, you’re expected to be at or descend to the published altitude before proceeding, ensuring you stay within the required airspace and can meet the next segment’s restrictions. So the purpose is to require altitude changes at those fixed points to maintain the intended vertical profile and constraints.