The Islamic State group claimed it had shot down an Iraqi military plane in the area, killing five crew members.
The military source said authorities had launched a search for the crew after the Cessna 208 Caravan went down near Kirkuk, around 220 kilometres (135 miles) north of Baghdad.
IS shoots down Iraqi army helicopter killing one
In a statement on Twitter, IS said it had shot down a military plane with anti-aircraft artillery and that it been on a bombing run against the city of Hawija, a stronghold of the extremists in Kirkuk province.
Iraqi forces have been making gains against the militants in recent months as they seek to reclaim territory seized by IS during a major offensive in 2014.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ