Fly expands on the blueprint of Wide Open Spaces, but the Dixie Chicks’ sophomore effort is invigorated by newfound confidence — even swagger. With the grit and gusto of roadhouse hell raisers, the trio pulls out “If I Fall You’re Going Down With Me,” “Sin Wagon,” and “Hole In My Head,” the last of which contains the refrain: “I need a boy like you like a hole in my head.” The Chicks don’t force themselves to choose between gutsiness and romance. Even the pop/country/bluegrass hybrids of “Ready to Run,” “Cowboy Take Me Away,” and “Without You” are underscored by a sense of wild mischief. And it’s impressive how many things the group does well. Their pop songs appeal to an audience of millions, while “Don’t Waste Your Heart,” “Hello Mr. Heartache,” and “Some Days You Gotta Dance” keep them rooted in the tradition of Hank Williams, George Jones and Buck Owens. The centerpiece of Fly is undoubtedly “Goodbye Earl,” a battered woman’s revenge fantasy which the Chicks handle with just the right note of fearsome glee.