A prisoner exchange between the Yemeni government and Houthi insurgents began Thursday based on an agreement reached last month after a week of negotiations in Switzerland.
Sources said planes took off from both Sanaa airport and from Sayoun airport near the central city of Marib.
The exchange involves the release of 1,081 prisoners in a complex operation overseen by the International Committee of the Red Cross over two days.
UN Yemen envoy Martin Griffiths, who attended last month's talks in Switzerland, hailed the successful start of the operation.
"Today's release operation, led by the ICRC, is another sign that peaceful dialogue can deliver," the envoy said.