Sanaa, Yemen (CNN)As the transport plane comes in to land at Sanaa Airport, the deep scars of the brutal conflict tearing Yemen apart are only too clear: wrecked aircraft line the runway, and nearby buildings lie in ruins. To most of the outside world, this war-torn country is off limits, the weeks-long battle between Houthi rebels and Saudi-led coalition forces making it too dangerous to visit, and a no-fly zone rendering its international airport all but obsolete -- but on Tuesday, CNN was granted rare access on a desperate aid mission by Unicef, the United Nations Children's Fund. The airport has previously been bombed. Hostilities are likely to resume before the day is out: a brief, peaceful window has been delicately negotiated following a special request from the U.N. -- but it won't last long. Unicef hopes there will be just enough time to deliver vital food and supplies, helping to ease the country's worsening humanitarian crisis. More than 100,000 Yemeni civilians have fled their homes since fighting began, and OCHA, the United Nations Office for the Coordination of Humanitarian Affairs, estimates that 15.9 million people here are in need of assistance. The main terminal at El Rahaba Airport is under the control of the Houthi rebels. We can't get near it for fear of provoking trouble. But there is plenty to be done out on the tarmac. Within minutes of touching down, a small army of aid workers is busy unloading huge mounds of much-needed provisions. Gusts of wind blow dust across the runway, as crates and pallets of emergency nutrition and medical equipment pile up rapidly beside the plane. Unicef's team has overcome more than one hurdle just getting it this far -- now they'll have to work out how to distribute it to those most in need in a country paralyzed by a lack of resources. Even before Saudi airstrikes, most of the 25 million people in Yemen required humanitarian assistance to meet their most basic needs, according to the United Nations. As they work, an Air India plane is taxiing away from the terminal. Thousands have fled the country on evacuation flights in recent weeks as the situation in Yemen has deteriorated. But for those who have nowhere else to go and no chance of a flight out, mercy missions by Unicef and other NGOs like it are the only hope. READ MORE: 'A window into hell' - desperate Yemenis flee by boatREAD MORE: Civilian catastrophe looming in YemenREAD MORE: Yemen crisis - how you can help . Bryony Jones contributed to this report .
Almost 16 million people in Yemen are in need of humanitarian aid, according to U.N.
Planeload of aid supplies including food and medicine was flown in to Sanaa on Tuesday .
A rare ceasefire was negotiated to allow the plane to land briefly .