Soaring worldwide demand for Boeing's workhorse, the 737, means the factory must increase its production rate by about four aircraft a month.

Already rolling off the line at a rate of more than one a day, the output has been increased to 35 planes a month. And further increases are already being planned for.

Beverly Wyse, VP and GM of the 737 program, says the increased output is necessary to meet customer demand for what is the most popular airplane in aviation history.

Boeing has taken a three-fold approach to prepare for the rate increases on the 737 program. The company is making production processes more efficient by working with employee process improvement teams, increasing the production capacity with capital investments such as a new wings system installation line in the Renton factory and making the site footprint more efficient by moving some production areas, expanding others and decommissioning outdated equipment.

A new automated spar assembly tool used to build the first spar is the ninth such machine at the Renton factory, drilling about 1,700 holes and inserting fasteners to make the spar. The tool increases the 737's wing-building capacity and is an example of one of many facilities changes happening at the Renton site to increase capacity and prepare for rate increases.

The 737 production rate will increase to 38 airplanes a month in the second quarter of 2013 and to 42 airplanes a month in the first half of 2014.