Can a plane fly without a transponder?
A transponder is not required unless an aircraft is operating: In Class A, Class B, or Class C airspace. Two‐way radio communications and operational transponder are normally required for operations within Class C airspace, but operations without radio communications or transponder can be conducted by LOA, facility directive, or special arrangement with Class C airspace controlling facility.
What causes a transponder to fail?
Problem: The most common reason for a transponder key not working is a dead battery inside the fob. If your key won’t unlock the doors or send a signal to the car, this is probably the culprit. One of the most common reasons for a non-functional transponder key is a dead battery. When the battery inside the key dies, the chip is unable to communicate with your vehicle’s ignition system. Start by carefully opening the key casing, and look for a small, flat battery.