Teams are working desperately to clear ash from Tonga's main airport runway in an effort to get vital supplies to the region following a volcanic eruption.
Some 200 people with wheelbarrows and shovels are sweeping the site so flights can deliver food and drinking water to the Pacific islands.
New Zealand and Australia have also sent ships in response to Saturday's eruption, which triggered a tsunami.
Three deaths have been reported - two nationals and a woman from Britain.
The Tongan government described the eruption, which sent plumes of gas, smoke and debris from the volcano up to 20km (12.5 miles) into the sky, as an "unprecedented disaster".
On Wednesday morning in Tonga, a UN representative for the region said that while clearing the ash on the main island of Tongatapu had proven more difficult than expected, good progress had been made and it was hoped that flights might soon resume.
"We thought that it would be operational [Tuesday], but it hasn't been fully cleared yet because more ash has been falling," Jonathan Veitch told reporters.
Mr Veitch praised the quick response of New Zealand and Australia in working to dispatch aid via navy ships, which he said had the ability to desalinate sea water and provide fresh supplies for the local population.
He said the vessels were carrying "a lot of our water and sanitation supplies" and described a "very challenging" situation on the islands.
New Zealand's Defence Minister Peeni Henare told the BBC the country had recently sent two naval ships that were due to arrive in Tonga in the coming days.
"It takes approximately three to four days to sail up to Tonga, and they'll have large provisions of water, food and medical supplies," he said.
Communications with the island chain has been majorly disrupted after the single underwater cable connecting Tonga to the rest of the world was severed in the eruption on Saturday.
Many Tongans abroad have since been waiting to hear news from loved ones.