Mohamad Gnounou, a spokesman for forces backing the GNA, said on Wednesday the forces have fully liberated Tripoli International Airport.
The operation to retake the country's largest civilian airport began Wednesday morning, with drones providing air cover, Gnounou added.
For the past two weeks, pro-GNA forces have been carrying out large-scale ground and air attacks, surrounding the airport area before the final assault on Wednesday, the spokesman added.
Pro-GNA forces "are chasing Haftar's militias, who are fleeing (southwards) towards Gasr Ben Gashir," Gnounou said.
Pro-Haftar forces have not commented on the setback, but the loss of the airport follows a string of defeats for Haftar in recent weeks.
The Tripoli Airport, in a strategic area on the capital's southern edges, has been closed since 2014 and had been seized by pro-Haftar forces last year.
Forces loyal to the east Libyan strongman have been battling since April 2019 to seize Tripoli from the UN-recognized GNA, in fighting that has left hundreds dead and forced 200,000 to flee their homes.
GNA forces buoyed by Turkish drones and air defense systems have taken back a string of coastal towns and a key airbase Haftar had used to launch attacks.
While the GNA is backed by Turkey, Haftar is supported by neighboring Egypt and the United Arab Emirates as well as Russia.
Libya has been mired in conflict since the 2011 uprising that toppled and killed longtime dictator Muammar al-Gaddafi, with two rival administrations and scores of militias struggling for power.