The airport -- largely destroyed by ISIS forces -- is now fully under Iraqi Federal Police control, said Col. Abdel Amir Mohamed, commander of the rapid response unit of the Federal Police.
Brett McGurk, the US envoy for the anti-ISIS coalition, congratulated Iraq for the victory.
"Congratulations to Iraqi forces for completing complex maneuver ops to secure #Mosul airport from #ISIS terrorists," he tweeted. "#ISIS is now trapped."
British Major Gen. Rupert Jones, deputy commander of Operation Inherent Resolve, offered a more muted assessment of the situation on the ground, telling CNN's Christiane Amanpour the airport was "reasonably well-secured."
"It's been a really good day," said Jones, speaking from Baghdad on Thursday. "The Iraqis are on the airfield. It looks reasonably well-secured."
"We should just be a little bit patient. It will really be for the Iraqis to say for certain once they're confident they're holding it," he added.
Iraqi forces launched a new bid to retake the western parts of the city on Sunday after declaring in late January that the east had been liberated.
- Warplanes bombed ISIS positions in the cities of Qaim and Hawija, as well as the Mansour district of western Mosul, killing at least 85 militants.
- Joint Operations Command says forces "killed many ISIS militants" and defused 60 IED.
- Iraqi forces have faced ISIS suicide car bombs and improvised explosive devices.
- Counterterrorism forces have stormed the al-Ghazlani military base west of the airport.
- There has been heavy fighting between Iraqi forces and ISIS at Mosul's main electrical power station.
- Residents say ISIS is searching homes for cell phones.
- Residents from eastern Mosul, under Iraqi control, send letters of support to the residents in the west.
Federal police and rapid response forces, backed by drones and heavy artillery, advanced from several positions to storm the airport, Lt. Gen. Raid Shakir Jaudat said in a statement. ISIS has held the airport since 2014 and has largely destroyed its infrastructure.
Sources have told CNN in recent months that ISIS has sabotaged the airstrip there to prevent its use.
The airport is on a large area of land in that city that is a symbolically important target for Iraqi forces. The area is an access point into the city from the southwest of the country. Taking it puts Iraqi forces in control of an area on the river's west bank for the first time.
Forces took the airport in a few hours and appear to be moving swiftly, taking back control of two villages -- Yarmouk and Tal al-Rayan -- near the airport and the al-Ghazlani military camp.
They have also taken control of an ISIS weapons storage warehouse, former ISIS headquarters and the barracks at al-Ghazlani, Brig. Gen. Yahya Rasoul, a spokesperson for the Iraqi operation, told CNN.
On top of that, the Joint Operations Command center reported that forces "destroyed many ISIS vehicles," defused 60 improvised explosive devices and "killed many ISIS militants."
But the push to take western Mosul is expected to take some time -- the east of the city took more than three months to take from ISIS control.
A city split
A resident of western Mosul told CNN that groups of ISIS fighters had been searching homes in one neighborhood near the river's bank, looking for cell phones and residents using them. ISIS forbids the use of cell phones and has executed residents in the past for using them.
ISIS frequently accuses residents of passing information to Iraqi security forces, and metes out harsh punishment to people caught using phones.
The east and west is divided by the Tigris River, and US-led coalition airstrikes have damaged all five bridges connecting the two sides in an effort to contain the militants in the west.
Residents of eastern Mosul have written letters of solidarity that the Iraqi Air Force dropped over western neighborhoods on Wednesday.
CNN went aboard an Air Force plane and met two residents of the east who had written some of the letters. One, Ghassan Mohammed Saadoun, said that he had received similar reassuring letters from other Iraqis when the east was being liberated.
He said ISIS had tried to confiscate those letters.
"I have lived that experience and seen these letters and leaflets, but ISIS tried to prevent us from seeing them as much as they can. When that happened, the children of ISIS went out into the streets and collected these letters early in the morning hours so no one could read them," he said.
One of the letters read: "Do not be afraid of the security forces -- they are coming to protect and to liberate you from injustice. Collaborate with them and don't be afraid of them. They are your sons. We wish you safety and security."
Another read: "We ask Allah to ease the pain that you are in. We pray to Allah to protect you. We ask you to please stay indoors for your safety when security forces arrive in your areas. Allah bless you our people."
Rights groups fear high death toll
Iraqi commanders say the battle for western Mosul will be the toughest fight yet against ISIS. Over the past two years, the militant group has dedicated much of its defensive preparation to the western part of the city.
The city has networks of alleys that are impassable by military vehicles. Human rights organizations fear that the use of heavy weaponry in the narrow streets of the old city -- where an estimated 650,000 civilians are still trapped -- would probably result in very high human toll.
Meanwhile, US troops operating around Mosul have been in exchanges of fire with ISIS, and some have been wounded in the last six to eight weeks as they have pushed closer to key front lines, military officials acknowledged.
A US defense official confirmed some had been injured on the battlefield, but declined to give numbers, saying that the injured had been evacuated from the battlefield.
The offensive to retake Mosul began in October in an extraordinary union of Iraqi troops and militia representing minority ethnic and religious groups that have often stood on opposing sides in Iraq's history.