Sept. 4 (UPI) -- United Airlines announced new routes in markets served by Spirit Airlines, as the later closed routes amid a bankruptcy filing. The new United flights will begin on Jan. 6 and will include additional service to Houston, Texas and Las Vegas, Newark, N.J., Columbia, S.C., Chattanooga, Tenn., New Orleans, Atlanta, Baltimore, Chicago and Florida cities Miami, Orlando and Fort Lauderdale. United has also announced new weekly flights between Houston and Guatemala City, Guatemala and