WASHINGTON — After American Navy destroyers fired dozens of cruise missiles at a Syrian airfield last month, fears emerged that Russia would respond by cutting off communications designed to prevent unintended confrontations in the skies over Syria, where both countries are conducting air campaigns.
More than six weeks later, however, the American and Russian militaries are still using a shared hotline to avoid conflicts involving their air operations over Syria. In fact, the number of calls has been on the rise.
“In the pure quantity of phone calls, it increased,” Lt. Gen. Jeffrey L. Harrigian, the top American air commander in the Middle East, told Pentagon reporters on Wednesday.
This does not signal that American and Russian diplomats are anywhere near agreement on how to end the conflict in Syria or on the future of President Bashar al-Assad. Rather, it indicates that both nations’ military officers are trying to manage the risks of an inadvertent conflict in the increasingly crowded airspace over Syria, which American and allied warplanes have shared with Syrian, Russian, Turkish and Israeli planes.
American and Russian officers started talking to each other after the Russian intervention in Syria began in 2015. The two sides do not coordinate strategy, but they have shared information to prevent midair collisions and other problems using a phone line that connects Al Udeid Air Base in Qatar, the command center of the American-led air war coalition, with the Russian base in Latakia, Syria.
The United States used the hotline to alert the Russians shortly before the April 7 attack on an airfield that Syrian planes had used to mount a chemical weapons attack that killed more than 80 civilians. As many as 100 Russian troops were believed to be at the airfield, though the Americans took pains not to target them, and none were hurt.
Angry that Syria, their ally, had been targeted, Russian officials threatened to suspend an agreement the United States and Russia had reached on flight safety.
But the Russians appear to have concluded that the cruise missile attack was a one-time operation and not the beginning of a broader military effort to dislodge Mr. Assad from power.
The American military wanted to keep the communications going so it could continue airstrikes against the Islamic State in Syria without coming under fire by Syrian or Russian air defenses.
“We have had to increase the amount of deconfliction work we’re doing with the Russians given the tighter airspace that we’re now working ourselves through,” General Harrigian said.
Tensions between the two sides remain. On May 9, a Russian fighter harassed an American KC-10 refueling tanker, an encounter that General Harrigian described as an “unprofessional” intercept. He said the American officers had raised the episode with the Russians, who acknowledged the problem.
Some of the conversations with the Russians, he noted, have been at relatively senior levels, led on the coalition side by a major general who serves as General Harrigian’s deputy.
Gen. Joseph F. Dunford Jr., the chairman of the Joint Chiefs of Staff, has also taken steps to expand communication with the Russians. Lt. Gen. Kenneth F. McKenzie Jr., the chief planning officer on the Joint Chiefs’ staff, has been talking to his Russian counterpart, General Dunford said last week.
The hotline figured in a recent episode in which a convoy of Shiite militia fighters that support Mr. Assad and are backed by Iran headed toward a garrison at al-Tanf, where American and allied Special Operations forces have been training Syrian fighters opposed to the Islamic State.
Armed with a bulldozer, an excavator and a tank, some of the militia fighters split off from the main group and began to build a small outpost that the Americans concluded was too close to al-Tanf for comfort. After warning shots failed to get the militia to leave, the Americans carried out an airstrike.
Now American officers are talking to their Russian counterparts, who they hope will dissuade the militia from trying something similar again.
“We’re continuing to ensure that, via the Russians, they understand our intent is for them not to threaten us,” General Harrigian said.