Boeing (NYSE:BA) took investors on a wild ride in 2020, with the stock losing 75% of its value early in the year but rallying partway back in the final months. As of the close of trading Wednesday, it was still down by about 32% for the year.

The aerospace giant's commercial aircraft arm suffered from a one-two punch. First came the grounding of its 737 MAX, and then the pandemic, which crushed demand for air travel, starved airlines of revenue, and caused carriers across the industry to scale back their growth plans.

Both of those issues appear to be resolving, though, and some investors are getting excited about the company again. Here's what to expect from Boeing heading into 2021.

The 737 MAX mess will linger

The troubles of the 737 MAX were weighing on Boeing well before the pandemic. The plane was grounded in May 2019 following a pair of accidents, and Boeing bled through more than $15 billion in cash in the first nine months of 2020 alone due to expenses related to the plane and the lack of revenue coming in while deliveries were halted.

The Federal Aviation Administration re-certified the jet in November, and Boeing soon after announced a massive order for it from one of its most important customers. But Boeing has hundreds of planes that it manufactured during the grounding that it needs to clear from its inventory, and not a lot of good options to place them.

A Boeing 737 MAX in flight.

Image source: Boeing.

Southwest Airlines, famously an all-Boeing fleet and holder of one of the biggest 737 MAX orders, is playing hardball with the company and trying to get planes on the cheap. Alaska Air Group, another stalwart customer (and based in the Puget Sound locale where Boeing makes the planes) submitted a relatively modest order for 23 of the jets. That's well below what analysts had expected it to order prior to the pandemic.

It's nearly impossible to overstate how important the 737 MAX is to Boeing. The various 737 versions make up 78% of its 4,240-plane contracted backlog, and most of those orders are for the MAX model. That amounts to more than $300 billion in future orders based on list prices.

At best, Boeing is going to need most of 2021 to work through the inventory it has built up; the company hopes to ramp up production to more than 30 airframes per month in early 2022. Prior to the issues, Boeing had expected to be manufacturing more than 50 planes per month by now.

The market for bigger jets has collapsed

For all the issues the MAX has, at least Boeing can take comfort in knowing that its smallish, fuel-efficient jet is in demand. The same cannot be said about many of the other planes in its portfolio.

As airlines recover from the pandemic, they are likely to focus heavily on domestic travel, and with passenger traffic not expected to return to 2019 levels for years, there won't be as much need for the twin-aisle jumbo jets that were once among the most lucrative for Boeing.

Boeing has cut its forecast for total deliveries over the next decade by 10% due to the pandemic, though it expects an eventual increase in demand, which is why it has kept its 20-year forecast steady. The iconic 747 will be discontinued, and a new version of its 777 has been pushed back by a year.

The 787 Dreamliner, which provided much-needed revenue in 2019 as the 737 MAX floundered, is also facing hard times. Boeing in early October announced plans to shutter one of its two 787 assembly lines and is cutting production from 14 planes per month to five.

In time, demand for international travel should rebound, and both the 787 and to a lesser extent the 777 should see sales rise again. But that will take time, and for now, the focus at Boeing remains on scaling back production rather than on ramping it up.

There is a ceiling on this stock

This aerospace powerhouse had a historically bad start to 2020, but it appears the worst is now behind it. The ingredients are in place for Boeing's share price to move higher in 2021. Still, I have no desire to buy in right now.

The company took on billions in new debt to give itself the liquidity to weather these dual crises. As a result, its net debt today is four times higher than it was prior to the 737 MAX grounding. Management is focused on paying down that debt, perhaps via a secondary stock offering, but the scars of 2020 will linger for some time.

BA Chart

BA data by YCharts

Boeing shares still look cheap relative to where they traded a few years ago, but it's worth remembering that those peak prices were achieved during a historic up-cycle in new plane sales. Factor in the added debt, and Boeing's current enterprise value is above where it has traded for most of the last decade.

Even if the worst is now over for Boeing, caution is warranted when considering the stock.

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.