The defense secretary took issue with multiple questions, at times talking over Senators at the hearing.
The Air Force's top uniformed leader said that planners need to consider vulnerabilities at military sites once thought untouchable by enemy forces.
This V-E Day marks the 80th anniversary of Nazi Germany's surrender to Allied forces.
The F-16s being shipped to Ukraine lack critical components like an engine and radar, the Air Force said, meaning they cannot be used operationally.
