Boeing has begun work on the first of the 737s that will roll out of the Renton factory at a rate of 38 per month.
The company gave reporters and photographers a look at the line Tuesday as production increases from 35 planes a month.
Boeing has a big backlog for the best-selling jetliner that was introduced in 1979.
The current version, called the next-generation 737, is the most widely flown jetliner in the world. Boeing plans to increase production next year to 42 per month.
By 2017 Boeing expects to start delivering the newest version, the 737 Max.