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For four dramatic days following the crash of Ethiopian Airlines Flight 302, as airlines and civil aviation authorities around the world grounded the Boeing 737 MAX, the question was: Would the US follow, and if so, when? Now Boeing, airlines and passengers are wondering: When will the Federal Aviation Administration, and its counterparts around the world, allow the plane back in the air?

The history of other groundings could provide an indication, as could a comment reportedly made by the FAA to US lawmakers. But a few airlines themselves, especially United, might quietly be providing some clues about their own expectations.

The 2013 grounding of the Boeing 787 Dreamliner lasted 123 days, four full months. On one hand, that was despite the fact that nobody had died aboard a Dreamliner, which could seem to presage an even longer MAX grounding. On the other hand, if — as regulators feared when they grounded the MAX — the MCAS flight-control system indeed contributed to the Ethiopian Airlines crash in the same way it seemed to have contributed to the October 2018 crash in Indonesia, Boeing might have fewer distinct issues to address with the MAX. With the Dreamliner, smoking batteries were the most prominent problem, but Boeing was simultaneously confronting other issues: reported fuel leaks and brake issues, among others. The previous high-profile grounding before that — of the DC-10 in 1979, after 273 people died when American Airlines Flight 191 crashed in Chicago — lasted 37 days.

Then there’s the news, as reported by ch-aviation (paywall), that the FAA expects the MAX to be grounded until mid-May “at the earliest.” That was according to the chairman of the US House Aviation Subcommittee, citing what the FAA had told committee members. To be clear, the FAA doesn’t seem to be predicting a return to service in May, only that the grounding will last at least until then, for a total of at least two months.

But what do airlines themselves expect? Public statements last week, such as investor updates, generally focused on the impact to airlines depending on how long the grounding lasts: United hinted it could be okay if the grounding doesn’t last too far into the summer, whereas Air Canada signaled it seems likely to be affected no matter what. But these statements didn’t attempt to actually predict how long the grounding could last.

TORONTO, ON- MARCH 13 - Air Canada Registration number C-GEHV which had just come in as Flight AC 758, from San Francisco, a Boeing 737 Max 8, is rolled out of the gate after being grounded, in Toronto. March 13, 2019. (Steve Russell/Toronto Star via Getty Images)An Air Canada Boeing 737 MAX 8 in Toronto on March 13, displaying the large engines that differentiate it from earlier-model 737s (Photo by Steve Russell/Toronto Star via Getty Images)

However, an analysis of schedule data in Diio Mi, a supplier of data to the airline industry, could indicate what airlines are thinking and how they’re adapting. So far, many haven’t loaded long-term schedule adjustments, instead merely removing MAXs from their schedules for the next week or two, even though the grounding will surely last longer than that. But FlyDubai, which planned to operate roughly 40 MAX flights per day in April, has removed MAXs from its schedule through April 15, more than a month after the grounding began. Russia’s S7 Airlines went further, conceding, via its updated schedule, that the MAX won’t fly through April 30.

United, meanwhile, has gone furthest with its published schedule adjustments — and, in doing so, has provided the first indication of how long a giant airline expects to be without the MAX. United has removed the MAX from its schedules all the way through June 5. Of course, that could turn out to be conservative. But United would probably prefer not to make a major change to its schedules twice, so it likely thinks there’s a better chance the re-entry into service will happen June 6 or later than before then. A re-entry into service on exactly June 6, although it’s unlikely to happen precisely then, would represent an 85-day grounding.

And why is United so confident it’ll barely be affected for now? Well, prior to the grounding, according to Diio Mi data, it had scheduled a total of 34,868 flights during a typical week in April, including 355 flights on its 737 MAX 9s. After the grounding? Exactly 34,868 flights during the same typical week in April despite the absence of the MAX from its fleet. How is that possible? Based on the schedule data, apparently United was able to absorb its entire schedule of MAX flights with its older Boeing 737-900s, the previous generation of the 737, which are configured with an identical 179 seats.

Being older aircraft, these 737-900s are what airlines consider “flexible capacity” — planes an airline flies as intensively as any others during peak periods but that it would park more during a lower-demand period. If United doesn’t need all of its planes during a non-peak period, typically it would keep its 737 MAX 9s flying as much as possible, because they burn far less fuel than its 737-900s. But come summer, it’ll press all of its 737-900s into full-time service, hence its statement that it could suffer more if the grounding lasts until then.

United is a massive airline with just 14 MAXs out of 777 total aircraft, or just 1.8 percent of its fleet. Air Canada, on the other hand, is merely a large airline with 24 MAXes out of 187 planes, or 12.8 percent of its fleet, so there’s probably no way it can absorb all those scheduled seats with other aircraft even now. Not to mention in the summer, when the highly seasonal airline needs to earn a lot of its money. This, in turn, explains why Air Canada’s financial update was less sanguine than United’s.

But at least Air Canada was a solidly profitable airline to begin with. For an unprofitable airline like Norwegian, with 36 MAXes and problems that began long before the MAX grounding — an airline that needs a strong summer more desperately than Air Canada — the question of how long the MAX will be grounded is an existential one.

Seth Kaplan is an aviation journalist. He is the transportation analyst for NPR and WBUR’s Here & Now, was the founding editor of Airline Weekly and is the author of Glory Lost and Found: How Delta Climbed from Despair to Dominance in the Post-9/11 Era.

Featured image of a United 737 MAX 9 by Zach Honig/TPG

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