Rebel forces in Libya have threatened to hit civilian planes flying over the capital Tripoli, declaring the city and its surrounding areas a "no-fly zone".
Mitiga, the city's only functioning airport, was closed on Wednesday after rockets were fired towards it.
But the UN-backed Government of National Accord (GNA) said it had now been re-opened.
Mitiga has been hit several times since Gen Khalifa Haftar began an offensive to seize Tripoli from the GNA.
In a statement posted on Facebook on Thursday, the GNA said resuming flights at Mitiga was of the "utmost importance".
It called on the UN "to shoulder its responsibility in this regard and to take serious and effective moves to ensure the safety of civilians and secure civilian aviation which faces a dangerous threat from attacking militias".
It came as top diplomats from Libya's neighbouring countries met in Algeria to discuss ending the conflict in the oil-rich country.
What did Haftar's forces say?
Gen Haftar's spokesman, Ahmad al-Mesmari, said in a statement on Wednesday that "any military or civilian aircraft, regardless of its affiliation, flying over the capital will be destroyed".
Mr Mesmari said Turkish soldiers deployed to support the GNA were using Mitiga as a base.
The warning came after Mitiga said it had suspended flights following a rocket attack on Wednesday that the GNA blamed on Haftar's forces.
The GNA branded the strikes a "flagrant threat" to the safety of air traffic and a "new violation" of a ceasefire agreed earlier this month.
Gen Haftar's forces did not immediately respond to the accusations, but did say they had shot down a Turkish drone after it took off from the airport.
Mitiga, a former military airbase, has been the only source of commercial flights in the city since Tripoli International Airport was heavily damaged in fighting in 2014.
The airport was re-opened on 14 January following months of closure prompted by repeated air strikes.
What's the background?
Libya has been wracked by conflict since the 2011 uprising which ousted long-time strongman Muammar Gaddafi.
The Libyan National Army (LNA), which is loyal to Gen Haftar, controls most of eastern Libya.
His forces launched an offensive against the capital in April 2019 but have been unable to take the city. Earlier this month, however, they did take the strategic city of Sirte.
According to the UN, tens of thousands of people have been displaced by the fighting around Tripoli.
The UN-backed government is supported by Turkey and its ally Qatar, while Gen Haftar is backed by Egypt and the UAE.
An internationally brokered ceasefire began earlier this month but within hours both sides accused each other of breaking it.
At a summit in Berlin last week, world leaders pledged not to interfere in the ongoing conflict and vowed to uphold a UN arms embargo. UN Secretary-General Antonio Guterres said major powers were "fully committed" to a peaceful resolution.