CNN  — 

Three Ukrainian pilots, including a well-known pilot who went by the call sign “Juice,” have died in a plane crash, the Ukrainian Air Force said on Saturday.

The incident occurred on Friday, August 25, near the city of Zhytomyr, about 140 kilometers (87 miles) west of Kyiv. The crews of two L-39 combat trainer aircraft collided in the sky while performing a combat mission, according to the Air Force.

The Air Force expressed condolences to the families of the deceased, saying that “this is a painful and irreparable loss for all of us.”

Juice was a MiG-29 pilot and part of a unit known as “Ghost of Kyiv” that defended central and northern Ukraine at the outset of the war.

In an interview last year with CNN’s Anderson Cooper, Juice said he got his nickname during a trip to the United States. He said his friends came up with the nickname, because he doesn’t drink alcohol and was always asking for juice instead.

Juice spoke to CNN again in June, explaining why he believed it was important for Western nations to provide Ukraine with American fighter jets.

“Our counteroffensive could be much more effective and much safer for our guys on the ground,” he said.

The circumstances of the crash are being investigated by the State Bureau of Investigation of Ukraine (SBI). In a statement released on Saturday, the agency said that special attention will be paid to the technical condition of the aircraft and whether flight preparation rules were complied with.

Specialists will also conduct a thorough diagnosis of the black boxes, the SBI said.

“The loss of each soldier is a huge loss for the whole country,” the bureau said.