Unfortunately it doesn't seem to actually do that. It does seem they load the expected route the aircraft is going to take but the position seems to be simply extrapolated based on time. A good way to see this is be on a flight that is supposed to have taken off awhile ago but didn't. I was on the ground for an hour or so while they tried to figure out some hydraulic issue and then returned to gate. FlightTrack showed us in the air. I wish. It ended up being a 7 hour delay.

It also isn't always very timely in updating on Android, so the information its displaying can be outdated. There is no way to force it to refresh Its a nice app, very pretty, but missing some very basic features that would make it more usable. Apple approach of simplicity vs. features that might be useful.