How should a controller phrase an instruction for maintaining a block altitude?

The instruction for maintaining a block altitude should clearly specify the lower and upper limits of the altitude range. Framing the instruction as "Maintain block from (lower altitude) to (upper altitude)" provides unequivocal guidance to the pilot about the specific altitude range they are expected to maintain. This phrasing enhances communication clarity, minimizing the chances of misunderstanding regarding altitude assignments.

Using precise language is crucial in air traffic control for safety and operational efficiency, especially when dealing with multiple aircraft operating in close proximity. This choice effectively communicates both the concept of a block altitude and the specific parameters, ensuring the pilot fully understands the expectations set by the controller. In contrast, other options may lack clarity or specificity, which could lead to confusion and potential safety issues in aircraft operations.