Ukraine’s air force chief was dismissed by President Volodymyr Zelenskyy, a day after the crash of a Ukrainian F-16 was made public.

Zelenskyy made the announcement Friday in a video address on the Telegram platform, saying it was important to strengthen the air force at the command level for the sake of national security and to reassure the population. A presidential decree on force commander Mykola Oleshchuk’s removal didn’t give a reason for his dismissal.

Ukraine said Thursday that one of its F-16 fighter jets crashed Monday during Russia’s biggest missile and drone attack on Ukraine since its full-scale invasion began February 2022. The United States has joined an investigation into what caused the crash.

Ukraine received its first consignment of F-16s in late July after a long debate among its Western allies about whether to supply the U.S.-made fighter jets.

Lt. Gen. Anatoliy Kryvonozhko was appointed acting air force chief, the Ukrainian army’s general staff said in a Telegram post.