Track line search is normally used when an aircraft or vessel has disappeared without a trace along a known route. As it is easy to plan and implement is used as an initial search effort. This search consists of a rapid and reasonably thorough search along the intended route of the distressed craft. Search maybe along one side of the track and return in the opposite direction on the other side (TSR). Otherwise search maybe along the intended track and once on each side, then search facility continues on its way and does not return (TSN). Aircrafts are frequently used for Track line search due to their high speed.
How much is the distance on each side between the track of the missing craft?