Three Ukrainian military pilots including a "mega talent" who yearned to fly F-16s were killed on Friday when two L-39 combat training aircraft collided over a region west of Kyiv on Friday, the air force said on Saturday.
President Volodymyr Zelenskiy, who is counting on swift training of crews to fly up to 61 F-16 fighter jets promised by his Western allies, said in his nightly video address that the three men included Andriy Pilshchykov, callsign Juice, "a Ukrainian officer, one of those who greatly helped our state."
Air force spokesperson Yuriy Ihnat described Pilshchykov -- who was fluent in English and aged 29 when Reuters interviewed him in December -- as a "mega talent" and leader of reforms, reports Reuters.
"You can't even imagine how much he wanted to fly an F-16," Ihnat wrote on his Facebook page. "But now that American planes are actually on the horizon, he will not fly them."
Ukraine's prosecutor general's office announced a criminal investigation had been opened into whether flight preparation rules were violated.
"It is too early to discuss details. Certainly, all circumstances will be clarified," Zelenskiy said.
The air force announced the crash on its Telegram app. "We express our condolences to the families of the victims. This is a painful and irreparable loss for all of us," it said.
Zelenskiy noted that the third Saturday in August is also when Ukrainian military and civilian aviation celebrate their professional day, and said the introduction of F-16s would mark a "new level" for military aviation.
"This will also bring civil aviation back to the Ukrainian skies, as it will move us closer to victory and provide Ukraine with greater security," he said.
Radio Svoboda shared video of blackened, mangled aircraft remains being removed from a field far from the frontlines at the village of Sinhury, about 10 kms (6 miles) south of Zhytomyr and about 150 kms (90 miles) west of Kyiv.
In the video, an unnamed man said he heard an explosion in the air above the school building and then two planes falling in smoke and flames. A woman described seeing two planes flying at a distance from one another then coming closer and closer to each other before the crash.
Military analyst and former pilot Roman Svitan, in an interview posted by online outlet Espreso TV, said the crash was "most likely" related to formation flying. He said the standard distance was 50-70 meters but that sometimes planes flew practically on top of each other at a distance of 3 to 4 meters.
He said the L-39 was at once a fighter, an attack aircraft, a bomber and a training plane but that in formation flying, especially at low altitudes, "there's no time for ejection."
Zelenskiy offered condolences to the pilots' families and added, "Ukraine will never forget anyone who defended the free skies of Ukraine."