Since the scroll-wheel is used by MS Flight Simulator, Flightplan does not respond to the mouse scroll-wheel. The map can be zoomed using the +/- buttons on the map itself to zoom in/out temporarily, or the GPS Follow zoom level can be set using the “Map Zoom” field. This is the zoom level that map will return to when GPS follow mode (circular “bulb” button, upper-left corner) is engaged or a waypoint is clicked.