Air distance from Seattle, USA to Castries, Saint Lucia is 4188.3 Miles (6740.4 Kilometers / 3637.1 Nautical Miles).
8 hrs, 41 mins is the flight duration between Seattle and Castries. 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.