Second Lt. Bryan Humphries, 31st Maintenance Squadron, cleans playground equipment at a park in Graf Ignatievo, Bulgaria April 22, 2012. More than 150 U.S. and Bulgarian air force members volunteered their off-duty time to refurbish playground equipment and build a soccer field at a village park. U.S. Air Force members are deployed from the 31st Fighter Wing at Aviano Air Base, Italy, to Graf Ignatievo Air Force Base to participate in Thracian Star 2012, a coalition training exercise geared towards strengthening partnerships and improving interoperability between NATO allies.