While Boeing’s planned production rate increase to 47 Boeing 737s a month in 2017 will add pressure on its suppliers, the bigger ramifications may come on the aftermarket side, an industry analyst suggests.

Boeing is already set to increase 737NG rates from the current 38 per month to 42 a month next year. The widely anticipated move to 47 each month, announced last week, will put more 737NGs into service faster as Boeing ramps up a new assembly line to start delivering the 737 MAX in 2017.

“We believe the supply chain has the step-up to 42 under control, but in general is stretched thin,” writes Canaccord Genuity analyst Ken Herbert in a research note. 

For some suppliers, turning up production rates is a matter of speeding up existing workflow. For others, like 737 fuselage supplier Spirit AeroSystems, new tooling must be put in place to accommodate the increase.

Herbert is among those who believe the 737 production rate will hit 50 or more per month once the transition to the MAX is complete, and assuming demand for the model continues to rise. Boeing’s 737 backlog sits at about 3,400—including 1,600 orders and memoranda of understanding for MAXs—and some customers, like Lion Air, cannot get them fast enough. 

While having more, newer 737s flying sooner is good news for Boeing, its suppliers and eager carriers, Herbert notes that the aftermarket may not have as much cause for celebration. 

“We believe that airlines are already slowing 737 maintenance spending as [production] rates have increased, and the useful life of the aircraft model continues to get shorter,” Herbert writes. “This [production rate increase] announcement will accelerate this process, especially if Boeing is able to maintain the higher 737 rate for more than just a few years.”

Boeing is among those refuting the notion that an aircraft’s useful economic life—generally pegged at 25 years—is shrinking. “Trends of the current-generation airplanes, such as the 737NG and [Airbus] A320, are in line with historical trends of their predecessors,” the U.S. manufacturer notes in a March 2013 study.

Comparing model-specific retirement trends from different eras is tricky, as factors ranging from demand for certain models and their parts to prevailing interest rates can influence whether an older aircraft stays in service or is retired. However, Aviation Week Intelligence Network’s (AWIN’s) Fleets database suggests that, on a per-airframe basis, 737NG retirements are following a different pattern than 737 Classics.

AWIN’s database lists 38 737NGs as retired, excluding accidents, write-offs and airframes used for testing, with an average retirement age of 11.7 years. From 2002 through 2007, the same database shows 39 737 Classics were retired, with an average age of 17.6 years. 

While the sample sizes are small, there is no disputing that the earliest 737 Classics flew longer than the first NGs built. Eleven of the 39 Classics retired by 2007 flew for at least 20 years. The oldest NG airframe will not reach its 20-year in-service anniversary until December 2017.