First, the reporting chain — Page 199, Lesson 295

I want to walk you through what happens when there's an act of unlawful interference on board an aircraft — hijacking, sabotage, or any deliberate unlawful act. This is a critical emergency procedure, and the regulations lay out very specific responsibilities and actions. First, the reporting chain. Following an act of unlawful interference on board his aeroplane, the commander — that's the pilot in command — is required to submit a report without delay to two authorities: the designated local authority, and the Authority in the state of the operator. If for any reason the commander is unable to do that, the responsibility falls to the operator. So the operator is the second line of reporting. Now, let's talk about the transponder — that's the equipment on board that transmits a four-digit code to air traffic control so they can identify and track your aircraft. In the event of unlawful interference in flight, the pilot in command shall endeavour to set the transponder to code A-7500. That's the international squawk code for hijacking. However, there's a nuance: unless the situation warrants the code A-7700. A-7700 is the general emergency code. So if the nature of the unlawful interference is such that a general emergency is more appropriate — for example, if there's a fire or medical emergency alongside the interference — you might use 7700 instead. But the primary hijack code is 7500. Now, what happens if ATC sees that code and asks for confirmation? If ATC requests confirmation of code A-7500, the pilot in command, if able, should confirm verbally the situation. But here's the key: if confirming verbally is not a viable option — for example, if the hijackers are listening and would react — the pilot in command should say nothing. And here's the critical part: ATC will take that silence as confirmation of the code. They will not ask again; they will assume the hijack code is genuine and initiate appropriate action in accordance with state procedures. Next, the flight path. Wherever possible, an aeroplane subject to unlawful interference shall be flown on the assigned track — that means you stay on the route ATC gave you — until ATC can be informed or until within radar surveillance coverage. The idea is to stay predictable and visible so ATC can track you. But if deviation from the assigned track is unavoidable — maybe the hijacker demands a different heading — and ATC is not informed, the commander is to broadcast warnings on the emergency frequencies unless circumstances on board dictate otherwise. So you try to get a warning out on 121.5 MHz or the appropriate VHF emergency frequency. The excerpt also says the use of transponder and any other system — specifically data link — should be considered. Data link is the text-based communication system, like ACARS, that can send messages without voice. That might be a way to communicate without alerting the hijackers. Now, if procedures have been detailed in Regional Supplementary Procedures — those are region-specific rules published by ICAO — they should be used if possible. But if no applicable regional procedures exist, then you have a specific altitude rule: proceed at a level which differs from normal IFR cruising levels by 500 feet, if the vertical separation minima is 1000 feet. Or, in areas where vertical separation minima is 2000 feet, you deviate by 1000 feet. So let me be clear: normal IFR cruising levels are based on magnetic track — odd thousands for easterly, even for westerly. Under unlawful interference with no regional procedure, you fly 500 feet away from that normal level if the standard separation is 1000 feet, or 1000 feet away if the standard separation is 2000 feet. That makes your aircraft stand out on radar as an abnormal track, alerting controllers that something is wrong even if the transponder code isn't set. So to summarise the key points: report to local authority and state-of-operator authority; set transponder to 7500 unless 7700 is more appropriate; if ATC asks for confirmation, either verbally confirm or say nothing as confirmation; stay on assigned track if possible; broadcast on emergency frequencies if you must deviate; consider data link; follow regional procedures if they exist; and if not, fly at a non-standard altitude offset by 500 or 1000 feet depending on the separation minima in that airspace.