In an aircraft cabin floor adjacent to the cockpit, a trap door opens downwardly into a security cell, to trap a terrorist trying to enter the cockpit. Two walls with lockable airtight doors bound a safety buffer cabin between the cockpit and the passenger cabin. Sensors like seat occupancy sensors, motion detectors, video cameras and microphones provide data regarding the location, movement and activities of passengers to a system that evaluates the data to recognize unusual data situations indicating one or more escalation levels of suspicious or aggressive actions by passengers. Alarm signals and terrorist countermeasure devices such as fogging or tranquilizer gas generators, noise generators, high intensity blinding / glaring lights, a cabin lighting master shut-off, window darkening devices, and tranquilizer dart guns are actuated automatically by the evaluation system, or manually by a cockpit input device or a portable signaling device carried by a flight attendant.