Random,
Perhaps along the lines of this article;
"More recently, a TSA-inspired Notice of Proposed Rule Making (NPRM) sought to create a rule requiring about 200,000 private airplanes to use a special anti-hijacking transponder – that is, one with a special button the crew could press should someone on board attempt to take over the flight deck.
Once activated, the transponder would squawk the international hijack code and could not be turned off or powered down by a cockpit circuit breaker."
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