Band leader Johnny Draper auditions his band, the Dixie Pixies, at the Eagle Aircraft Co., hoping to be hired to play for the workers in the plant. However, personnel manager E. V. Hartley can only offer them regular jobs, and when Johnny inspires the Dixie Pixies to work in the plant, lead singer and dancer Donna D'Arcy leaves the band for a singing job at the Club Martel in downtown Los Angeles. Johnny is assigned to be an apprentice welder to Lee Davis, whom he discovers is a tough female welder, while trumpeter Jeep Jackson pushes the candy cart through the factory. Lee has a chip on her shoulder from being heckled because of her job, and becomes enraged when Johnny publicly makes fun of her while the band rehearses during their lunch break. Johnny and the band members are switched to the swing shift so that they can host a dance starting at midnight and give the late-night workers a boost. The dance is a great success and Johnny is startled to find that Lee, whom he had only seen in a welder's mask, is a beautiful blonde. When Lee drives him to Club Martel to try to convince Donna to rejoin the band, Donna becomes jealous of Lee and introduces her to the audience as the "freak of the week" because of her profession. Lee makes an impassioned speech about women, like herself, who have taken work in defense plants to support the war effort and, after singing a song, runs out humiliated. Donna now refuses to rejoin the band until it has become famous. News of Johnny's swing shift band, called the Jive Bombers, spreads to the trade papers, and when a public show hosted by the plant is planned, Jeep, who is dating riveter Mariposa Ginsbotham, encourages Johnny to ask Lee to sing for the band. Although they got off to a bad start, Lee and Johnny make up, and she agrees to sing. During a final rehearsal, however, Donna offers to return to the band and, despite the fact that he has fallen in love with Lee, Johnny feels it would be in the best interests of the band to highlight Donna. Backstage during the show, Johnny tries to convince Lee that he made the right decision by making her watch Donna so she can see that she is truly a professional. Donna later admits to Johnny that she did not return to the band for him, but for the potential of success, and he now feels free to propose to Lee. Johnny is delighted when he gets a contract for the band to appear in New York, but Lee refuses to join them, preferring to stay and do her part to keep the American war planes flying. Johnny realizes she is right, and the band agrees to give up their big break to support their country.