ATC ON, ATC ALT, TA ONLY????? So what is the correct transponder setting for ground operations? FAA SAFO 15006 dated 5/19/15 tells us the following: "Nationwide, airports with ASDE-X report an average of twenty non-compliance transponder events per day, even with airport diagram or Automated Terminal Information Service (ATIS), or both, verbiage directing pilots to operate with transponders on. To proactively address these problems, aircraft operating on all airport movement areas at all airports, not just those that are ASDE-X equipped, must have their transponders on in the altitude reporting mode." From this information we can assume we should operate our transponder in the ATC ALT mode when operating on the airport movement areas.