The missiles have targeted coalition aircraft at least six or seven times since the official end of hostilities on May 1, the official told AFP.
However, the coalition tally is said to be far lower than the actual number, a humanitarian agency official told AFP.
There have been at least 19 surface-to-air missile attacks on planes flying into Baghdad international airport since May, the humanitarian official said, requesting anonymity.
The failure to secure the area around the airport has been one of the main reasons for the delay in the airport's opening for commercial travel, with the exception of chartered flights for diplomats, aid workers and journalists.
Russian-made SAM-7s are the missile of choice in Iraq, the coalition official said.
On Wednesday, US military spokesman Lieutenant Colonel George Krivo said 320 SAM-7 missiles have been turned in to the coalition, which is paying 500 dollars for every one handed in.
The weapons are evidence of the abundance of readily available arsenal left behind in Iraq with the collapse of Saddam Hussein's regime.
Lieutenant General Ricardo Sanchez, the top US military commander in Iraq, conceded last week it was impossible for his soldiers to fully guard the hundreds of weapons depots remaining from Saddam's time.
The US military seizes major weapons caches every day, including plastic explosives, ammunition, mortars, rocket-propelled grenades and surface-to-air missiles, without making any real dent in the ability of Saddam loyalists and other resistance fighters to battle US soldiers.
Shoulder-fired surface-to-air missiles have been used by international terrorist groups. Last November, two SAM-7s were fired at an Israeli jetliner flying out of Mombasa, Kenya, but missed their target, in an attack that was timed to coincide with a car bomb at a hotel resort.