The suspension of the memoradum of understanding (MoU) signed in 2015 on the air operations immediately broke out tensions in the skies over Syria.

Later Friday, the Russian Defense Ministry announced that it has officially informed the United States that it is suspending its obligations under the memorandum at midnight.

Under the accord, the two countries have exchanged information about flights by a U.S.-led coalition targeting the Islamic State and Russian planes operating in Syria in favour of the Assad government. Moscow was suspending the accord, the Defense Ministry said, because it sees the U.S. strike “as a grave violation of the memorandum.”