Transportation Security Administration chief John S. Pistole on Thursday welcomed the unionization of his agency's 47,000 airport screeners. The move has proved controversial, with critics arguing that, as a security agency, TSA should not allow collective bargaining. (Associated Press)

Transportation Security Administration chief John S. Pistole on Thursday welcomed the unionization of his agency's 47,000 airport screeners. The move has proved controversial, with critics arguing that, as a security agency, TSA should not allow collective bargaining. (Associated Press)