Nonstop is a little less than 5 hours.
That will depend on where you are flying from. If you are flying from the U.S. it will take 5 hours on average.
From bilbao, Spain to Barbados is 17 hours 45 minutes. Source is expedia.com
It varies a lot, depending on the company and the "scales or air flight", i.e., stops, and delays in airports. Minimum: 15h22min Maximum: 28h48min .
According to HowManyHours, about 9 hours.