President Barack Obama boards Air Force One at the Pulkovo International Airport in Saint Petersburg on September 6, 2013, as he leaves for Washington, DC, after attending the G20 summit. World leaders at the G20 summit today failed to bridge their bitter divisions over US plans for military action against the Syrian regime, with Washington signalling that it has given up on securing Russia's support at the UN on the crisis.(JEWEL SAMAD/AFP/Getty Images)