Deconfliction line
A deconfliction line is an official line of communications established between militaries who are or could be hostile, to avoid dangerous misunderstandings and miscalculations based on ignorance. The ultimate aim is to avoid accidents and conflict escalation. In the 2010s and 2020s, the US and Russia set up deconfliction lines during  the Syrian civil war and Russo-Ukrainian War. They were regularly tested by military staff, and used by air traffic controllers and senior military officers. They were used to avoid midair collisions between aircraft in the same or adjacent airspace, and sometimes to give warning of airstrikes. In April 2017, Russia severed the Syrian line in retaliation for a called strike. See also

 2015 Russian Sukhoi Su-24 shootdown, a motive for establishing the Syrian deconfliction line
 September 2016 Deir ez-Zor air raid
 Line of communications
 Moscow–Washington hotline
 Russia–Syria relations
 Wagner Group activities in Syria

References

Military terminology
Telecommunications
Military
Syrian civil war