What is block altitude in air traffic control terminology?

• A. A specific altitude assigned as a minimum safe altitude.
• B. The altitude above which the aircraft must cruise.
• C. A block of altitudes assigned by ATC to allow altitude deviations.
• D. An altitude used for takeoff procedures.

Answer: (C)

Block altitude is a defined range of altitudes that ATC assigns to a flight to allow the aircraft to maneuver vertically within that range without needing a separate clearance for every small change. This flexibility helps maintain spacing and efficiency when winds, weather, or traffic require occasional climbs or descents. As long as you stay within the assigned block, you can adjust your altitude as needed; moving outside the block would require updated ATC clearance. This concept differs from a single minimum safe altitude, which is about terrain clearance, from a cruising altitude which is a specific target for en route flight, and from takeoff procedures, which specify initial climb and obstacle clearance rather than a range for ongoing vertical maneuvering.