One often gets satellite images of contrails and it’s hard to visualize what’s going on, especially with racetrack contrails drifting in the wind. So I wrote a little contrail simulator applet to demonstrate the formation of a contrail under various conditions.
I have just updated this applet to display contrail grids by default. There are just two flight paths that intersect, and the grid forms as the contrails from those two paths are blown by the wind.
To get the racetrack simulator, uncheck the “intersection” checkbox in the lower left.
This video demonstrates this effect in the real world