The station keeping, or now FFS I guess, was really quite interesting. One the screen, you have a grid box with dots. There is the centerline which is the lead aircraft. You select the dot and the aircraft maintains that position, over up, over down, etc. Was really quite interesting, and entirely automated.
As gums noted, they did realize quite the fuel savings by staying in the uplift part of the vortex.
I am not sure of the disconnect capability if something goes wrong with the lead aircraft...
EDIT: The Autonomous Formation Flight system marries an extremely robust flight control and guidance system with a close-coupled GPS/IMU placed on the aircraft. Inter-ship communication allows the multiple GPS/IMU systems to share state data and through and extended Kalman filter technique, they yield a differential carrier phase solution. They resolve the relative position accuracy between the aircraft in formation to less than 10 cm.
Through shared state data, the guidance systems aboard the aircraft resolve coordinated trajectories that permit the aircraft to maintain formation. The trailing aircraft is thus capable of maintaining its position within the lead aircraft’s wing tip vortex with extremely high accuracy.