Air distance from Seattle, USA to Saint-Denis, Reunion (French) is 10576.4 Miles (17021 Kilometers / 9184.5 Nautical Miles).
21 hrs, 57 mins is the flight duration between Seattle and Saint-Denis. This is the In-The-Air flight time. You should also add the taxi time, airport wait times and possible delays due to bad weather, etc. for the total flight duration time.