It doesn't matter how sick you are, how much money you have or who you know — you cannot get a commercial flight out of Yemen's main airport.

Key points: Access to the airport has been restricted for the past 12 months

Access to the airport has been restricted for the past 12 months Yemen's other airports are a 'risky' 10-to-20-hour drive away from the capital

Yemen's other airports are a 'risky' 10-to-20-hour drive away from the capital Closure traps millions of people, prevents free movement of commercial, humanitarian goods

Access to Yemen, classified as the world's worst humanitarian disaster, is heavily restricted and for the past year its main airport has been forced shut by a Saudi-led coalition that has been bombing the country.

That has slowed down aid, trapped millions of people and stopped commercial activity.

The United Nations has called for the Saudi-led coalition to ease its 12-month blockade of Yemen's main airport so the sick and injured can get out and aid can get in.

Care International's Wael Ibrahim, the country director in the Yemen capital Sanaa, described the blockade as "collective punishment for people in Yemen".

"There is absolutely no justification for the airport to continue to close," he said.

"It serves no purpose except people's suffering."

Yemen's 20 million people are on the brink of famine. ( Supplied: Care International )

The Saudi-led coalition that has been bombing Yemen shut down the Sanaa airport a year ago because it was in a territory controlled by its opponents, the Houthi rebels, claiming it needed to be closed due to security concerns.

Since then the only flights the Saudis have allowed in and out of the airport are UN, Red Cross or Médecins Sans Frontières (MSF) humanitarian flights.

Trapping the sick, preventing aid deliveries

Yemen's other airports are a 10-to-20-hour drive away from the capital, a trip Mr Ibrahim described as risky, involving crossing several frontlines.

"There is the risk of you travelling through where there are different armed groups and be subject to harassment, or worse," Mr Ibrahim said.

"You can never know if your name is on some list and if somebody is looking for you.

The trip to alternative airports, up to 20 hours away, involves crossing several battle fronts. ( Supplied: Care International )

"In addition to the considerable time that it takes them — it's a rough journey."

But the airport's closure does not just trap millions of people, Mr Ibrahim said it also prevents the free movement of commercial and humanitarian goods.

"The commercial sector is unable to bring in goods, unable to bring in medical supplies, bring in money," he said.

"Sick people are unable to travel for medical treatment."

Crucial aid now has to go through several diversions before it can get to where it needs to go.

"Each flight takes lots of logistics and additional cost, because we have to charter planes rather than be able to use the commercial flights that used to come regularly to Yemen," Mr Ibrahim said.

A country on the brink of famine

The closure comes as Yemen is on the brink of famine, with 20 million people in need of food aid. One in three children have severe malnutrition and the health system is collapsing.

The Yemeni Ministry of Health estimated 10,000 people had died because they could not get specialist treatment inside the country, nor could they be flown out to other locations.

The UN says Yemenis have been living in a "fortress mentality" since the airport was shut down. ( Supplied: Care International )

Jamie McGoldrick, the UN's top aid official in Yemen, said the UN had been lobbying the Saudi-led Coalition and Yemen's exiled Government in Aden to reopen the airport.

"We continue to advocate to all the parties involved in this and the people who control the airspace, the people in Riyadh, the people in Aden, to help alleviate the suffering," he said.

"It's like being caught up in a fortress mentality that you can't escape from.

"This has become a tactic of the war in itself and I think [it] is really unfair.

"It's important that the international community hears about it — this is yet another aspect to how difficult it is to live or work or breathe in the Yemen context."

He said if the Saudis insist security remains the issue, all patients could be checked on the way out.

"Even we would like to propose, and we have done, to have a humanitarian flight once or twice a week to allow patients to come out," Mr McGoldrick said.

"They would have to stop off in Saudi Arabia anyway and be seen in terms of who is on that plane in terms of if it can go on further.

"So for us it would be an easy way to alleviate the suffering of many people here who need medical treatment."

The Saudi-led coalition has not yet responded to the UN proposal.