What happened

Investors are getting excited about the potential relaunch of Boeing's (NYSE:BA) 737 MAX, which is expected to be recertified in the coming weeks, if not sooner.

That's good news for Boeing, but also really good news for suppliers that count on the MAX for revenue. Shares of Parker-Hannifin (NYSE:PH) finished Thursday up 9.6%, Spirit AeroSystems Holdings (NYSE:SPR) was up 8.7% on the day, and Allegheny Technologies (NYSE:ATI) was up 7.7%.

So what

The 737 MAX has been grounded since March 2019 following a pair of fatal accidents. The company has continued to produce planes through much of the grounding, but at reduced levels.

That's caused ripples through the supply chain, and put companies that count on the 737 MAX for a significant portion of their revenue in a difficult spot. Spirit AeroSystems, a former Boeing subsidiary, makes the plane's fuselages, while Allegheny and Parker-Hannifin make components for the plane and its engines.

A Boeing 737 MAX in flight.

Image source: Boeing.

At long last it appears the 737 MAX will soon fly again, with regulators in the U.S. and Europe closing in on certifying the changes Boeing made to try to solve the software problems that led to the crashes. Boeing will need years to work through the inventory of more than 400 planes that have been built but not delivered over the last year or so, but it hopes to get back to a production rate of more than 30 airframes per month by 2022.

Cowen analyst Cai von Rumohr earlier in the week upgraded Spirit to an outperform, calling it the best way to invest in the 737 MAX return. Prior to the grounding, the 737 MAX was Spirit's largest, most profitable program, accounting for nearly half of its revenue in 2018. 

Although neither Allegheny nor Parker-Hannifin have that same level of exposure, they both will benefit from getting the plane flying again.

Now what

The 737 MAX's return to service is good for Boeing and its supply chain, but investors should not expect an overnight turnaround. Boeing still has that substantial inventory of planes to work through, and with airlines cutting flights due to the pandemic, demand for new airplanes is at a decade low.

The suppliers are in the early stages of a recovery, but it will take years to play out. In the meantime, I'd advise investors to consider other avenues to invest in a potential 737 MAX and commercial aviation recovery, and watch these turnarounds play out from the sidelines.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.