In air traffic control, separation is the name for the concept of keeping an aircraft outside a minimum distance from another aircraft to reduce the risk of those aircraft colliding, as well as prevent accidents due to wake turbulence.  Air traffic controllers apply rules, known as separation minima to do this. Pairs of aircraft to which these rules have been successfully applied are said to be separated: the risk of these aircraft colliding is therefore remote. If separation is lost between two aircraft, they are said to be in a conflict.