Boeing is telling customers and suppliers that the 737 MAX will not receive its first regulatory approvals until “mid-2020,” which all but ensures MAX operators will not have the aircraft before the peak mid-year travel period ends.

The update estimate—which Boeing cautions is neither concrete nor blessed by regulators—”is informed by our experience to date with the certification process,” Boeing said in a statement.

“In order to help our customers and suppliers plan their operations, we periodically provide them with our best estimate of when regulators will begin to authorize the ungrounding of the 737 MAX,” the Chicago-based company said Jan. 21. “We are informing our customers and suppliers that we are currently estimating that the ungrounding of the 737 MAX will begin during mid-2020.”

The move means that initial revenue-service operations may not start until September or later—weeks longer than the most conservative airline estimates. U.S. carriers have pulled MAXs from their schedules until early June but will almost surely push this out further in the coming days.

U.S. airlines will be among the first to have regulatory clearance to put MAXs back into service, as the FAA will lead global regulators in un-grounding MAXs, possibly joined by a few others. Executives with U.S. carriers have estimated that they will need 30-60 days from the FAA’s approval to prepare MAXs for service, train pilots and work the aircraft back into flight schedules. 

American Airlines, Southwest Airlines, and United Airlines had MAXs when the 387-aircraft fleet was grounded in March 2019. Alaska Airlines was supposed to get its first MAXs in mid-2019. 

Airlines in other countries must wait for their regulators to lift the groundings, with some agencies pledging to take independent looks at Boeing’s work and FAA’s approvals. It is not clear whether the ongoing FAA review is giving other regulators time to complete some of their independent work, or if any time line slippage in the U.S. will be mirrored around the world.

Boeing stopped delivering MAXs following the grounding and paused production this month.

Boeing’s estimates are the only data points industry has to go on. The company in 2019 made public return-to-service approval estimates as part of its effort to project how much it would owe affected customers based on how long the MAX was out. After months of repeating projections that turned out to be inaccurate—Boeing believed the MAX would be approved by the end of 2019—FAA Administrator Steve Dickson told former Boeing CEO Dennis Muilenburg that the agency, not the company, is in control of the process, and there is no time line.

Word of Boeing’s latest projection was reported by several news outlets, prompting the company to issue its statement.

The FAA has not changed its stance. “We continue to work with other safety regulators to review Boeing’s work as the company conducts the required safety assessments and addresses all issues that arise during testing,” the FAA said, repeating a now-common refrain. “We have set no time frame for when the work will be completed.”

The next major step on the MAX’s approval path is a certification flight, which is not scheduled. The latest projection was not driven by any new findings linked to Boeing’s MAX changes and training revisions, a source with knowledge of Boeing’s thinking said. Rather, it reflects the reality of the certification process’s pace and accounts for some additional schedule slippage. A recently discovered software issue played no part in Boeing setting the mid-year estimate, the source added.

The latest change reflects the high levels of uncertainty surrounding the MAX situation, even among well-connected customers. Southwest’s move to clear MAXs until early June came on Jan. 17, suggesting Boeing’s thinking changed in recent days.

On the production front, Boeing has said that re-starting MAX work in its Renton factory will not necessarily be tied to initial regulatory approvals. The OEM plans to focus on clearing the undelivered backlog and may wait until it has a better idea of when other regulators will lift their operations bans, clearing the way for customers to begin accepting deliveries again.