A three-day prisoner exchange between Yemen's warring parties began on Friday as 318 prisoners were released, the International Committee of the Red Cross said at the end of the operation's first day.
About 70 prisoners were travelling from the rebel-held capital Sanaa to Aden, the government's temporary base, on two flights, with 250 being sent from Aden to Sanaa on board a Yemenia flight.
More than 500 detainees will be transferred on Saturday, said Fabrizio Carboni, the ICRC's regional director for the Near and Middle East.
"So we reach more or less 900 detainees at the end of this operation," he said.
US National Security Adviser Jake Sullivan welcomed the exchange on Friday evening.
"This breakthrough prisoner exchange is being overseen by the ICRC and was the result of many months of constructive engagement and mediation overseen by the UN’s Special Envoy for Yemen, Hans Grundberg," he said.
"The United States is proud to support this UN-led engagement and we will continue to do all we can to help consolidate the truce that has now been in effect for over one year, helping to set the conditions for a more enduring peace.
The past year in Yemen has been the quietest since the war began, Mr Sullivan said, saving thousands of lives and allowing for vast increases in humanitarian assistance, fuel imports, and civilian flights to and from Sanaa.
"Building on the prisoner exchange today, we encourage all parties to further consolidate these positive trends and ultimately forge a diplomatic resolution to the conflict," he said.
The first flight from Sanaa took off at about 10am local time on Friday carrying 35 prisoners, while the second, from Aden to Sanaa, took off at 11am with 125 prisoners on board, the ICRC told The National.
Mahmoud Al Subeihi, the country's former defence minister, and Nasser Mansur Hadi, brother of former president Abdrabbuh Mansur Hadi, who had been detained since 2015, were among the prisoners being released from Sanaa.
A red carpet and military salute welcomed the former officials when they landed in Aden at about noon.
Footage from the airport showed people dancing in celebration.
Mr Hadi will be travelling onward to Riyadh for medical treatment later on Friday, a government source told The National.
"This comes at a time of hope for Yemen as a reminder that constructive dialogue and mutual compromises are powerful tools capable of achieving great outcomes," UN Special Envoy to Yemen Hans Grundberg said in a statement.
“A sight for sore eyes,” said Yemeni conflict analyst and former Houthi detainee Hisham Al Omeisy.
“I remember how my kids rushed to me when I was released and there was no feeling in the world to top the relief and happiness felt.”
More ICRC flights carrying prisoners are scheduled on Saturday, including from Sanaa to the Saudi capital, Riyadh, as well as from the southern Saudi city of Abha to Sanaa, and between Sanaa and the Yemeni city of Mokha on the Red Sea coast.
There will be flights both ways on Sunday between Marib, capital of the eponymous Yemeni province, and Sanaa.
"ICRC teams will accompany the detainees, overseeing the transfer and addressing any medical needs," ICRC spokeswoman Jessica Moussan said in a statement on Friday.
The Yemen Red Crescent Society and Saudi Red Crescent Authority will also play "vital roles", Ms Moussan said.
"Their medical staff and volunteers will be present at the six airports to help infirm detainees on and off the planes and provide first aid and ambulance services."
The prisoner exchange is one of several recent developments that have raised hopes of a long-term truce between the Saudi-backed government and the Iran-backed Houthi rebels that could pave the way for talks on a political solution to end the civil war in Yemen.
Saudi ambassador to Yemen Mohammed Al Jaber visited Sanaa this week with officials from Oman to discuss renewing a UN-brokered truce that expired in October.
The Saudi ambassador left on Thursday after several days of negotiations, a Yemeni government official confirmed to The National.
Pro-Houthi official Mohammed Al Bukhaiti told Reuters that the talks were "going well".
The talks are also expected to cover the reopening of all Yemeni ports, releasing all prisoners of war, and unifying the two central banks under the rebel and government administrations.
Another Houthi official, Abdulmalik Alejri, said on Twitter that "with determination and honest intentions remaining difficulties can be resolved".