It is part of a major runway and taxiway upgrade project for the two international airports, the country's largest, by the Ministry of Transport.

In Noi Bai, both runways will be upgraded, three new rapid exit taxiways will be built and existing taxiways will also get upgrades.

Indication lights, a drainage system and other flight management facilities would also be installed.

The work will cost VND2.03 trillion ($87.4 million).

The Civil Aviation Authority of Vietnam (CAAV) has said that the runways would be closed one at a time.

The flight frequency would decrease as a result, To Tu Ha, deputy director of the airport, said.

Though the total number of flights per day would stay the same, some scheduled for peak hours would be shifted to less busy hours, he said.

"Passengers need to closely follow the information provided by airlines and come to the airport at least two hours before their flights."

Noi Bai is entering its peak summer schedule with 400-450 domestic flights on average and over 60,000 passengers going through it daily, Ha said.

Similar work will be undertaken at Tan Son Nhat with the only difference being only one of its two runways will be upgraded. It will cost VND2.015 trillion ($86.7 million).

It would be more difficult to close down runways once flight frequencies go back to normal levels after the Covid-19 pandemic is over, the ministry said.

International flights remain suspended since late March.

Since 2017 Noi Bai and Tan Son Nhat airports have been chronically overloaded and receiving new-generation aircraft with huge loads, which has degraded their runways and taxiways.