The purpose of this study is to evaluate the safety and efficacy of the Relay thoracic stent-graft system to treat thoracic aortic aneurysms. Efficacy will be evaluated by the device-related adverse event rate of endovascular repair (via Relay Thoracic Stent-Graft) through 1-year. Safety will be evaluated by comparing major adverse events through 1-year in subjects treated with the Relay Thoracic Stent-Graft to those who underwent surgical repair. Long term follow-up is conducted through 5 years.