The precautionary move, revealed in statistics made public by the command on Saturday, was taken as Russian officials have threatened to suspend the communication line the American and Russian militaries use to notify each other about air operations in Syria.

So far, the Russian military does not appear to have taken any threatening actions, such as directing its battlefield radar or air defense systems to confront the Americans, or carrying out aggressive actions in the skies, United States officials said.

But officials who spoke on the condition of anonymity to discuss internal planning said the commanders needed time to determine whether the Syrian president, Bashar al-Assad, and the Russian military would treat the American cruise missile strike as a one-time operation that they would not respond to militarily. As a precaution, the Pentagon is flying patrols in Syrian skies with F-22 jets, the Air Force’s most advanced air-to-air fighter.