President Volodymyr Zelensky of Ukraine dismissed the head of the country’s Air Force on Friday, days after the crash of an F-16 warplane in what may have been a friendly fire incident.

A Western official who has been briefed on the preliminary investigation in the air crash said that there were “indications” that friendly fire from a Patriot missile battery might have brought down the jet, though mechanical failure and pilot error have not been ruled out.

The dismissal of the Air Force commander, Lt. Gen. Mykola Oleschuk, announced by the president in a post on the Telegram social media app, is the second high-profile departure this year. In February, President Zelensky dismissed Ukraine’s top military leader, Gen. Valery Zaluzhny, replacing him with Gen. Oleksandr Syrsky.

Mr. Zelensky gave no specific reason for the decision, which came one day after the Air Force had announced the loss of the F-16, but said that it was necessary to strengthen military leadership. “We need to get stronger,” he said. “And we need to take care of people. Take care of the personnel. Take care of all our soldiers.”

The plane crashed on Monday while defending against an intense aerial attack by Russian forces, which on Friday hit an apartment block in Ukraine’s second-largest city, Kharkiv, killing at least six people and wounding scores more, local authorities said.

The possibility of friendly fire incidents becomes especially acute during mass attacks by missiles and drones, military experts say.