“U.S. and Russian forces operating in Syria have increased the use of the deconfliction hotline — a communication line opened to avoid midair collisions and reduce the potential for miscalculation by forces operating in Syria, according to Air Force Lt. Gen. Jeffrey Harrigian, commander of U.S. Air Forces Central Command.”
Source: US increases use of deconfliction hotline with Russia amid pending operation to liberate Raqqa