In hijack scenario, altitude deviation: The correct step is to continue at altitude that differs from semicircular rule with 1000 ft above FL290 and 500 ft below.

• A. Fly the emergency triangle
• B. Declare an emergency
• C. Continue at an altitude that differs from the semicircular rule with 1000 feet when above FL 290 and 500 feet when lower than FL 290
• D. As soon as possible commence emergency descent in order minimise the difference between cabin pressure and outside pressure

Answer: (C)

In this scenario the maneuvering principle is to break away from the standard altitude pattern to reduce predictability and maintain smoother, more controlled management of the situation. The semicircular rule sets the usual cruising altitudes based on direction, but in a hijack situation the instructions are to keep an altitude that intentionally differs from that rule. The specified offsets—1000 feet above the altitude dictated by the semicircular rule when you’re above FL290, and 500 feet below when you’re below FL290—provide a deliberate, predictable margin from normal assignment without creating an abrupt or unsafe profile. This helps keep the flight controllable and reduces the hijacker’s ability to rely on standard altitude expectations while ATC coordinates a response.

Other options don’t fit this specific control objective. Flying an “emergency triangle” isn’t a recognized step tied to altitude deviations during hijack procedures. Declaring an emergency is important in many situations, but the question targets the altitude-deviation action chosen for hijack scenarios. Starting an emergency descent to minimize cabin pressure differences would be inappropriate here, as abrupt descent can escalate risk to everyone on board and doesn’t align with the prescribed altitude-offset response.