Ukrainian President Volodymyr Zelensky honoured the memories of three pilots killed in a plane crash on Ukraine's Aviation Day.
The accident occurred on Friday in the western Ukrainian region of Zhytomyr, though it was only reported on Saturday by Ukrainian media.
"My condolences to the relatives and confidants, to all those who knew the young men," Zelensky said on Saturday in his daily video address.
The victims included well-known fighter pilot Andriy Pilshchykov, who made a powerful contribution to Ukraine's air defence as the country fends off Russian attacks, the president said.
Zelensky vowed there would be a thorough investigation into the incident.
For Kiev, the reputation of its fighter pilots is of great importance. Ukraine has been pushing its international allies for months to supply it with modern, US-made F-16s to help fend off Russia's invasion.
Kiev has received commitments from several countries to train their fighter pilots and provide the warplanes.
Zelensky focussed on the ongoing fighting at the front during his video address. He thanked the soldiers for their commitment at the various combat sections, highlighting the fighting around Bakhmut in eastern Ukraine and near the village of Robotyne in the south of the country.
He did not provide details on developments on the front line.
