Sept. 28 (UPI) -- Six U.S. Air Force F-16 fighter planes joined Bulgarian aircraft in a four-week air policing mission over Bulgaria, NATO announced on Monday.
The F-16 Fighting Falcons of the 555th Fighter Squadron, 31st Fighter Wing, stationed at Aviano Air Base in Italy, were deployed to Graf Ignatievo Air Base, near Plovdiv, on Monday after completing the "Thracian Viper 20" international training exercise at the Bulgarian airbase.
"NATO air policing missions are designed to secure the airspace of allies. The air policing jets will take to the skies at short notice when military or civilian aircraft are in distress or they do not follow international flight regulations and approach the sovereign airspace of NATO allies," a NATO statement on Monday said.
Policing missions have been in place in Eastern Europe since 2004. Missions in southeastern Europe intensified in 2016, after Russia's 2014 intervention in Ukraine and its annexation of Crimea.
Six CF-18 fighter planes of the Royal Canadian Air Force are currently operating in neighboring Romania.
"In the fall of 2016, the Bulgarian Air Force conducted successfully for the first time a joint mission with their U.S. colleagues," a statement on Monday from the Bulgarian Defense Ministry said. "Participation in such joint missions enhances the Air Force capabilities to safeguard the integrity of allied airspace.
In 2017, Italian fighter planes were part of the mission in Bulgaria.
Bulgaria, a NATO member since 2004, is rapidly modernizing its military force. The air force began training with F-16 planes in 2019, after eight F-16s were purchased at a cost of $1.2 billion.