SINGAPORE, June 14, 2016 (Xinhua) -- A Republic of Singapore Air Force (RSAF) CH-47 Chinook helicopter hanging the Singapore national flag flies in formation with two RSAF AH-64 Apache helicopters during a practice for national day celebrations in the southern sky of Singapore on June 14, 2016. Singapore will celebrate the national day on August 9. (Xinhua/Then Chih Wey)
