Although the work is rarely dramatic, it demands constant attention, disciplined cross-checking, and close coordination between the pilots and air traffic control. Once accepted, the crew is expected to maintain these parameters with a high degree of precision unless air traffic control approves a change. Over the North Atlantic, predictability is essential because aircraft are separated by procedural standards rather than continuous radar observation. The foundation of the crossing is the North Atlantic Organized Track System (NAT OTS). Any requested changes must first be approved by oceanic air traffic control.