A freak transport error threatens to derail Boeing 737 production temporarily, raising questions once more about supply chain vulnerabilities as commercial aircraft production rates climb ever higher.

Boeing was still evaluating as this article went to press the impact of a train derailment in Montana on 3 July that dislodged six 737 fuselages en route to final assembly in Renton, Washington, from the Spirit AeroSystems factory in Wichita, Kansas.

Montana Rail Link, the railroad company involved in the derailment, had recovered three fuselages that had slipped down a steep embankment into the churning Clark Fork River. Pictures from the scene showed the three fuselages had sustained severe damage.

Boeing was still assessing the extent of the damage and how it will impact a production system that rolls-out six completed 737s every three working days at current rates.

It is a system designed to accommodate a minimum of disruption from a globally scattered supply chain, with parts flowing into Renton by air, sea and rail.

Spirit, which Boeing divested in 2005, builds 70% of the 737 – the forward and aft body, nose section, nacelles, pylons, vertical fin, horizontal stabiliser, flaps and wing-to-body fairing – at its sprawling production facility in Wichita.

Spirit ships the complete fuselages – lacking wings, landing gear and most systems – by train to Renton. The freight cars pass through Kansas City, Nebraska, Wyoming, a journey of nearly 2,000nm (3,700km) through mostly remote plains and wilderness.

The latest derailment is the most significant disruption in modern memory. In 2011, a tornado dislodged two 737 fuselages from a train passing through Nebraska. The following year, damage caused by another tornado closed Spirit’s factory in Wichita for a week.

Somehow, the storm ripped off a section of the factory’s roof, but did not cause any damage to the fuselage structures lying below. Spirit took several weeks to fully recover, but never missed a “load date” for a 737 fuselage in Renton.

The latest incident again highlights Boeing’s heavy reliance on Spirit for a 737 product line in a market segment with unprecedented demand.

Boeing plans to raise 737 output again to 47 aircraft per month in 2017, a 12% jump from the current rate of 42 every month. At current production levels, two assembly lines in Renton each complete one 737 roughly every working day. Boeing is opening a third line in 2015 in the same factory to build the 737 Max, creating capacity to more than 60 aircraft per year.

Source: Cirium Dashboard