When creating an overlay AFCAD file for an airport, does that overlay need it's own control tower or, since it is just a slightly modified copy of the primary airport, will it use the ATC from that airport? I did not create a control tower for my overlay and watched the flight through FSUIPC's TrafficLook until it got within a few nm of the airport. At that point the flight dissapeared, then moments later I saw the plane on the ground at the gate.GW

The overlay needs to have a tower and ground frequency. They can be the same as those for the primary airport, or different. If they're the same, ATC will interleave the messages just fine.