Lyrically, Paper Airplane is a somber affair, but there are plenty of tempo variations; songs such as bluegrass-infused kicker "Miles to Go" and the traditional Irish sounding "Bonita and Bill Butler" are plucky enough to pass for happy-go-lucky if you don't listen too closely to the words. But when Krauss and Union Station really start to wallow, it's intoxicating: "Paper Airplane" is a stunning song about a relationship's end, and it serves as the perfect foil for Krauss' delicate voice, while the cover of Richard Thompson's "Dimming of the Day" will break your heart upon the first listen.