What this relates to
To facilitate the safe navigation of aircraft in controlled airspace, national authorities specify vertical and horizontal distances, known as separation standards. The standards ensure safe separation of aircraft. Aviation terminology refers to undershooting of the separation standards as a separation minima infringement (SMI).
Example
Two aircraft start one after the other from the same airport on the same route. The private jet is faster than the commercial aircraft in front of it and catches up to it. For a brief moment, they undershoot the separation standards. The air traffic controller instructs the private jet to correct its flight path, thereby ensuring that the separation of the two aircraft is safe again in accordance with the standard.
