BRUSSELS, July 22 (Xinhua) -- The air forces of Romania, Greece and the United States took part in the annual multinational air exercise "Thracian Star 2016" in the Bulgarian skies, NATO said in a press release Friday.
Led by the Bulgarian Air Force, the 11-day flying activity during the exercise concluded Thursday.
The main exercise objectives are to achieve greater interoperability in operations and to further improve capabilities and skills of operators in a NATO environment.
The Thracian Star multinational exercise series has been held annually under an agreement on defense cooperation between the United States and Bulgaria. The event has been expanded to include Bulgaria's neighboring countries.
Multinational exercises of allies highlight forces that are capable of operating alongside each other during combined operations, the security organization said.