The Twin Otter was and is used by dozens of airlines and militaries around the world, and was produced in three main series (100, 200, 300) until 1988.As of 2006, over 40 years after design and manufacturing work on the original DHC-6 began, more than 500 of this aircraft were still flying. In that year Viking Air purchased the type certificate for the DHC-6 and announced its intention to offer a new build Series 400 Twin Otter.