Extension: The extension will assess long-term safety and tolerability of omaveloxolone (RTA 408) in qualified patients with Friedreich's ataxia following completion of Part 1 or Part 2. Patients will not be unblinded to study treatment in Part 1 or Part 2 upon entering the extension study. Patients will receive open-label omaveloxolone (RTA 408) at 150 mg once daily.