A fragile UN-brokered truce between the Yemeni government and Huthi rebels hung in the balance Wednesday as talks on renewing it hit trouble, threatening the humanitarian gains of the past two months. Aid agencies and Western governments have urged Yemen’s warring parties to extend the truce, which has significantly reduced the intensity of fighting in a conflict the United Nations says has triggered the world’s worst humanitarian crisis. But with just one day before the truce expires, there was no sign of any breakthrough in UN-backed talks. A Yemeni aircraft left the rebel-held capital Sanaa for Cairo on the first commercial flight between the two cities since 2016, the latest gain from the truce deal. The office of the United Nations special envoy for Yemen told AFP there were 77 people on board the Yemenia flight from Sanaa airport, which has been closed to commercial flights for nearly six years. It is the seventh such flight since the truce went into effect on April 2. The six previous flights had all been to the Jordanian capital Amman. Yemen has been gripped by conflict since the rebels overran Sanaa in 2014, triggering a Saudi-led military intervention in support of the beleaguered government the following year. On May 16, a Yemenia plane carrying 126 passengers, including critically ill hospital patients and their relatives, became the first commercial flight to leave Sanaa since August 2016. Air traffic into the rebel-held capital has been largely halted by a Saudi-led blockade, but there have been exemptions for aid flights that are a key lifeline for the population. Despite accusations of violations from both the Saudi-led coalition and the Huthi rebels, the truce has significantly reduced levels of violence. The Huthis have said they are considering renewing the ceasefire amid UN efforts to extend the truce. But on Tuesday, the United States warned the truce talks were in “trouble” as it pushed for an extension to help support millions of people at risk.