President Barack Obama said today he will nominate retired Army officer with intelligence community experience to lead aviation security efforts amid concerns about passenger planes being bombed or hijacked, Reuters reported. Obama chose retired Major General Robert Harding to head the Transportation Security Administration after his first pick, Erroll Southers, withdrew from consideration when Republicans questioned whether he would try to unionize the workforce that screens travelers and luggage at U.S. airports. "I am confident that Bob's talent and expertise will make him a tremendous asset in our ongoing efforts to bolster security and screening measures at our airports," Obama said in a statement. Harding previously served as deputy to the Army's chief of intelligence and as director for operations in the Defense Intelligence Agency. After he left the Army, he started his own security advisory firm, which he sold in 2009. "The TSA administrator is among the most important unfilled posts in the Obama administration," Janet Napolitano, head of the Department of Homeland Security, which includes the TSA, told reporters and urged the Senate to act on his nomination quickly.