"The fact that they (Russian bombers) use Iranian airspace continues because we have total strategic cooperation with Russia," Admiral Ali Shamkhani told the Fars news agency.
Shamkhani is secretary of the Supreme National Security Council and Tehran's coordinator of political, security and military actions with Russia.
"The use of Iranian airspace by Russian aircraft is made subject to a joint decision, taking into account the need... to fight terrorism," he told the IRNA news agency.
He said Russian planes had not recently needed to land in Iran for re-supply.
Iran and Russia are closely cooperating in Syria and provide political, financial and military backing to the regime of President Bashar al-Assad.
Tehran has sent military advisors and "volunteer" fighters to support the Syrian military in its fight against rebel and jihadist groups.