When ACARS is unavailable, monitor which frequencies?

• A. ARINC or ATL radio
• B. VOR
• C. ILS
• D. Transponder

Answer: (A)

When the data-link for ACARS is down, you switch to voice communications to stay connected with ATC and coordinate your flight. The back-up channels specified are ARINC and the ATL radio, which are the voice circuits tied to the ARINC network and ATC facilities. Monitoring these allows you to receive and transmit clearances, route changes, and other essential instructions in real time, keeping operations safe and compliant until ACARS is available again. The other options serve navigation or surveillance functions rather than backup communications: VOR and ILS provide navigation guidance, and the transponder handles radar reporting—none of these provide the ATC voice link you need when ACARS is unavailable.