Plane vs Train Security

You can't use a train as a weapon, other than targeting a train station, but one has access to the train station before the train, so...
Trains usually don't travel close enough to densely populated areas.
You know where they are at all times, and can redirect them at will.
A plane blows up in mid air, everyone dies; a train, maybe you kill a car full, maybe a few more if the train derails.
The psyche/economic impact: the number of people who travel on airplanes is much higher than the people who travel by rail.

That's what comes to mind...