The UN World Food Program(WFP) on Thursday sent a first plane loaded with medical supplies for developing nations especially vulnerable to the coronavirus pandemic, aiming to ramp up the service to 350 flights per month.

WFP chose nine airports across the world to take part in the special humanitarian air bridge, which will transport medical and humanitarian teams from early May.

A Boeing 757 cargo flight left Belgium's Liege Airport on Thursday evening loaded with 16 tons of medical supplies, including masks, gloves, medicines and syringes for the West African country of Burkina Faso.

The grounding of commercial passenger flights during the pandemic has not only prevented tens of thousands of humanitarian workers from travelling but removed cargo space.

"Today (the challenge) to find cargo planes is nightmarish. Prices have gone up by four or five times," said Amer Daoudi, WFP's COVID-19 corporate response director. "You also might not get it today or the day after or for a week."

So WFP, which serves as the logistics arm of the UN system, has locked in contracts for an extended time to ensure its flights operate and do so at a reasonable cost.

"We need capacity to service many of the fragile countries across the globe. This air bridge is going to cover almost 120 countries," Daoudi said.

Daoudi envisages the flights will run for about three to four months, but could be extended. The airlift would be stood down if viable commercial alternatives returned.

The transport is available for all humanitarian health workers and cargoes. Thursday's supplies were destined for the UN children's agency UNICEF and the International Committee of the Red Cross (ICRC) in Burkina Faso.

The other hub airports are Accra, Addis Ababa, Guangzhou, Johannesburg, Panama City, Shanghai, Subang and two in Dubai.