Boeing plans to begin production of the first 737 MAXs, to be used for flight testing, in 2015. Pictured here is an artist’s rendering of Boeing’s 737 production line in Renton, Wash., with capital investments in place to support production at a rate of 42 airplanes a month and the introduction of the 737 MAX. The MAXs will be built on the “proving line” in-between the two main production lines to the left and the right.