#1. It looks like you enabled the option to “show departure and arrival airport” on the map configure window.
The blue line is an estimate of the route the aircraft has taken.
The actual route may be different…
Because, acarsd plots a direct route between received position reports.
With #1 enabled, if the airports appear on the map and the acars message contains routing information,
acarsd will draw a line from the departure airport to arrival airport and the aircraft will be plotted along that line.
The current position report is the red point.
Previous position reports, including departure/arrival airports, are the white points.
Acarsd just connect the points.
Aircraft, like cars, use a map, charts, with routes instead of roads.
So another position report along a previous line, route, is common.
Once a year our local airport has an open house and they give away, free, New York State aeronautical charts.
Contact your local airport to see if they have an open house. They may not offer free charts but I don’t think one would cost much.