Iraq's militarised police forces have entered Mosul International Airport, taking over the runway amid fierce clashes with Islamic State fighters, according to officials.
The advance is part of a major assault that started five days ago to drive IS militants from the western half of Mosul, Iraq's second-largest city.
Two officers said the airport buildings are under fire from federal police forces, and troops from the US-led coalition are with the advance.
Special forces troops had earlier joined the government offensive to push the militants out of the western half of Mosul, reaching a sprawling, IS-held military base on the city's southern edge as police forces advanced towards the airport.
From the south, the elite counter-terrorism forces reached the Ghazlani base in the morning hours, officers said, adding that fierce clashes were under way at the base perimeter.
The advances come days after Iraqi forces officially launched the operation to take Mosul's western half, with regular army and federal police forces taking part in the initial push.
Since the operation began on Sunday, Iraqi forces say they have retaken nearly 50 square miles south of the city.
"The counter-terrorism forces will be an additional force which will expedite the liberation of Mosul's western side," said Brigadier General Yahya Rasool.
The battle for western Mosul, the extremist group's last major urban bastion in Iraq, is expected to be most daunting yet.
The streets are older and narrower in this section of the city, stretching west from the Tigris River that divides Mosul into the eastern and western half.
The dense urban environment is likely to force Iraqi soldiers to leave the relative safety of their armoured vehicles, and the presence of up to 750,000 civilians will also pose a challenge.
Mosul fell to IS in summer 2014, along with large areas of northern and western Iraq.