Iraq inspected an Iranian cargo plane bound for Syria on Monday, a day after it searched a Syrian aircraft flying from Moscow to Damascus, the head of Iraq's civil aviation authority said.
No prohibited items were found on either flight, Nasser Bandar told AFP.
Washington has for months accused Baghdad of looking the other way as Tehran sends military equipment through Iraqi airspace to Syrian President Bashar al-Assad's forces, and has called on Iraqi authorities to make random, unannounced inspections.
Iran has described the inspections as "unacceptable" and has officially protested to Baghdad, describing the searches as part of "an Iranophobia project sponsored by the United States, Western countries and the Zionist (Israeli) regime and certain regional countries."
Tehran has remained a steadfast ally of Assad regime despite the bloody conflict with Syrian rebels seeking his overthrow, which the United Nations says has killed more than 70,000 people since it erupted in March 2011.