The UN special envoy to Yemen, Martin Griffiths, welcomed the arrival of the second medical evacuation flight late on Saturday to transport critically ill patients to Jordan.
The flights, referred to as a “medical bridge”, began last Monday. They are seen as a humanitarian breakthrough in the five-year conflict, which erupted after the Iran-backed Houthi rebels overran the capital Sanaa in 2014.
A Saudi-led coalition intervened in the conflict on behalf of the internationally recognised government in March 2015 in an effort to curb rebel gains.
“Together with the first flight, which arrived in Amman Monday, the Medical Bridge has so far transported 31 Yemeni patients to receive life-saving medical care currently unavailable in Yemen,” Mr Griffiths’ office said on Twitter.
The plane transported 22 Yemeni civilians who are in dire need of medical treatment, the World Health Organisation said.
“The second group are ready to start their journey of hope and recovery as they begin receiving the medical care they urgently need,” the WHO said on Twitter.
The flight had been expected to leave Sanaa airport on Friday but was rescheduled for “technical reasons,” the WHO said.
It said on Friday it was “committed and working very hard to ensure these Yemeni patients receive the treatment they need".
Among those who left Sanaa was Ayman, 10, who suffers from scoliosis.
“He urgently needed surgery not available in Yemen to prevent his organs from being severely affected and let him have a normal life,” the WHO said.
“I’m ready for the operation,” Ayman said. He dreams of becoming a football player, he said.
The re-opening of Sanaa’s airport and flights are part of the UN’s confidence-building measures between the warring sides in Yemen.
The measures are aimed at resuming political talks to end the conflict.