The unexpected removal of more than 400 new narrowbodies from the global fleet via the Boeing 737 MAX grounding is sure to have repercussions in the aftermarket, but predicting them is proving challenging.

Regulators grounded the 376-aircraft MAX fleet in March after the second fatal 737 MAX 8 crash in less than five months. Adding in the 30-40 MAXs per month that airlines would add under normal circumstances, and the global fleet is managing the unexpected unavailability of more than 400 aircraft and counting.

Many of the new MAXs were slated to help airlines grow, but a notable amount—perhaps 40%—were replacing older narrowbodies. If airlines timed the retirements to come when planned airframe or engine maintenance was due—as most do—not getting a new MAX would likely leave them down an aircraft.

“There are no drop-in CFM56 overhaul slots available, unless you want to pay through the nose,” one industry analyst said. 

Procuring parts could be a problem as well. 

“Sourcing critical parts was already a challenge, and this [MAX grounding] doesn’t help,” one source noted. “You can’t just start producing life-limited parts.”

The consensus among industry executives queried at Aviation Week’s MRO Americas is that, aside from extending leases or adding lift with short-term leases for the few available narrowbodies, operators are sticking to their fleet plans, including retirement schedules.

Boeing’s announced 737 production-rate reduction from 52 to 42 per month will not ease supply-chain pressure. Most suppliers, including engine OEM CFM International, will continue to work at a 52/month rate. This will keep the pressure on the front of the supply chain, where castings and forgings specialists have been stressed for some time. 

Any retirement delays that the MAX saga creates would only add to the problems. Used-parts availability for the most popular engine platforms, including the CFM56 and International Aero Engines V2500 is already scarce, and not having the MAX push some older 737s and Airbus A320s out of the market will exacerbate the issue.

Boeing is working to get 737 MAX software and training updated in a package that regulators will approve before clearing the fleet to fly again. The return-to-service timeline is not clear, but most expect the fleet to be grounded well into May at least. Any longer and operators will face the challenge of getting through the peak summer season shorthanded.

Sean Broderick,