The aircraft, operated by Greater Pioneer Operating Company (GPOC), crashed in Rubkona County, Northern Unity State, while carrying 19 people, including two crew members.
Two individuals who were scheduled to be on board did not take the flight, and one person survived, bringing the confirmed death toll to 18.
Authorities have yet to release an official passenger list, but officials said Indian and Chinese nationals were among the victims. The sole survivor is receiving medical treatment.
The crash has sparked mourning across South Sudan, particularly in the oil sector and among affected communities.
“In the wake of this tragic incident, I have instructed the Ministry of Transport and all relevant authorities to conduct a thorough and swift investigation to determine the cause of the crash and provide answers to the grieving families,” Kiir said in a statement.
Kiir described the crash as a national tragedy affecting not only the victims’ families but also the oil industry and the country at large.
“It is with profound sorrow that I learned of the tragic plane crash that claimed 20 lives,” he said. “Among the victims were engineers and technical staff from GPOC, one of our major oil joint ventures.”
The president called for unity in supporting the bereaved families and honoring the victims.
“While we pray for the survivor’s swift recovery, I extend my deepest condolences to the bereaved families, GPOC staff, and all those affected. May you find strength during this difficult time,” Kiir said.
Authorities have not yet disclosed preliminary findings on the cause of the crash.