For altitude constraints described as 'at or above', which altitude should be used for MCP control?

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Multiple Choice

For altitude constraints described as 'at or above', which altitude should be used for MCP control?

The main idea is that when you have an altitude constraint described as “at or above,” the altitude you use for MCP control is the altitude you are ATC cleared to maintain—the clearance altitude. The constraint on the procedure sets a minimum crossing height, but your actual autopilot target is governed by ATC clearance, not the upcoming or published constraint alone. If you’re cleared to a certain altitude, you keep that altitude on the MCP until you’re cleared to descend further or the procedure requires a change that ATC authorizes. The constraint at a fix simply ensures you don’t descend below that minimum by that point; it’s a condition you must meet, not the immediate MCP target. So you would set the MCP to your clearance altitude, and let the flight management system manage when and how to meet the constraint as you progress. That’s why the correct choice is the clearance altitude. The next altitude constraint, the active leg altitude, or the altitude published by the procedure are not the primary reference for MCP control when ATC clearance takes priority and constraints are described as “at or above.”

The main idea is that when you have an altitude constraint described as “at or above,” the altitude you use for MCP control is the altitude you are ATC cleared to maintain—the clearance altitude. The constraint on the procedure sets a minimum crossing height, but your actual autopilot target is governed by ATC clearance, not the upcoming or published constraint alone.

If you’re cleared to a certain altitude, you keep that altitude on the MCP until you’re cleared to descend further or the procedure requires a change that ATC authorizes. The constraint at a fix simply ensures you don’t descend below that minimum by that point; it’s a condition you must meet, not the immediate MCP target. So you would set the MCP to your clearance altitude, and let the flight management system manage when and how to meet the constraint as you progress.

That’s why the correct choice is the clearance altitude. The next altitude constraint, the active leg altitude, or the altitude published by the procedure are not the primary reference for MCP control when ATC clearance takes priority and constraints are described as “at or above.”

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