That is the optical illusion part of the incident. The contrail from the plane is expanding over time, so the farther away the plume is, the larger it is.
Our minds are accustomed to the idea that bigger means closer and smaller means farther away. This makes people interpret the plume as moving away from them when it is actually moving towards them.
Interesting. I find it interesting, also, that everyone was afraid that it was retaliation for the devaluation of the dollar by Obama. It shows how worried people are about Obama’s policies.