You could run PlanePlotter and use a conditional expression to post an alert when one is seen.http://www.coaa.co.uk/planeplotter.htm
While this is true, I'd either need to run it on my pi (which already complains often that it can't run MLAT) or another piece of hardware. Since this installation is outdoors running in my barn, the additional hardware option isn't really a viable option.
Eh, I guess it doesn't really matter. I thought it'd be a cool idea, but if there is no interest, then it's not worth the effort even if the data is already available.