Which measure best helps prevent unauthorized flying of aircraft?

• A. Post warning signs at the hangar door.
• B. Park disabled vehicles around the aircraft.
• C. Remove batteries but leave the aircraft accessible.
• D. Install hidden shutoff switches, park disabled vehicles around aircraft, and remove batteries.

Answer: (D)

Preventing unauthorized aircraft operation requires layered security that blocks access, power, and movement. Installing hidden shutoff switches makes start procedures harder to execute because the switches aren’t obvious, so a would-be operator can’t simply flip a visible control to energize the aircraft. Parking disabled vehicles around the aircraft adds a physical barrier and signal that the aircraft is not ready for use, which disrupts attempts to move or tow it. Removing batteries eliminates the primary power source for most systems, preventing the aircraft from powering up and starting.

Doing all three together covers different angles of attack—controls access, blocks power, and hampers movement—so it’s far more effective than any single measure. Warning signs alone rely on compliance and can be ignored; relying on a single measure like parking other vehicles or removing batteries leaves gaps that an unauthorized user could exploit.