The Boeing 737 Max won't resume flying in the US before 2020

• United Airlines announced on Friday that it would extend Boeing 737 Max cancellations until at least January 6.
• American Airlines recently announced it was pulling the plane from its schedule through January 15 - and expects to begin reintroducing it the following day - while Southwest Airlines previously said it would pull the jet through January 5.
• Regardless of when the FAA re-certifies the plane, it will not return to passenger service with US airlines in 2019.
• Boeing said it expected to submit its final proposed software fix to the FAA in September, with approval expected in the fourth quarter. Reports suggest Boeing has not yet submitted the fix.
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United Airlines announced on Friday that it was extending cancellations of the Boeing 737 Max through January 6, 2020, as global regulators continue to review proposed software and flight computer fixes to the troubled plane.

United pulling the 737 Max from its schedule until at least early January means that the jet is guaranteed to remain out of passenger service among US airlines through the rest of 2019. American Airlines recently announced that it would pull the plane from its schedule through January 15, 2020, while Southwest Airlines - the biggest 737 Max operator in the US - previously pulled the jet from its schedule through at least January 5, 2020.

Boeing had previously said in the summer that it expected to submit its final software fix to the FAA in September, and for the plane to be re-certified to return to service at some point in the fourth quarter, possibly early November.

However, it was unclear whether it met that expected September submission timeline - the Seattle Times reported in October that the fix had not been submitted yet. Clearance from the FAA to resume flights could come within about a month of submission, after the final software fix is assessed by regulators and test flights are conducted.

Global regulators may follow the FAA's findings and re-certify the plane quickly, or may take longer to perform their own inspections and test flights.

Even if the plane is recertified in 2019, it will likely take airlines longer to install the software and prepare stored planes to fly again.

American Airlines said on Wednesday that it expects the Max to be recertified near the end of 2019, and to gradually phase the Max back into commercial service beginning on January 16, 2020, following installation of the new software and various tests and inspections.

Airlines have been forced to cancel thousands of flights as the grounding has continued - United said it expects to cancel 93 flights per day in November and 75 in December due to the grounding, while American said it would cancel about 140 daily through December. American also said it would use older 737-800 aircraft - which are not included in the grounding - to operate flights whenever possible.

The FAA said that it would "follow a thorough process, not a prescribed timeline, for returning the aircraft to passenger service."

Read more: The complete history of the 737 Max, Boeing's promising yet problematic workhorse jet

Although Boeing has not shared an updated timeline for the jet's return, there have been indications that it expects the plane to return to service relatively soon. Boeing previously said it was hiring temporary employees to help prepare stored planes for delivery once the grounding lifts, and recently began reaching out to retired former airline employees.

The 737 Max has been grounded since March, following the second of two fatal crashes in five months.

Preliminary reports into the two crashes that led to the grounding - Lion Air Flight 610 and Ethiopian Airlines Flight 302 - indicate that an automated system erroneously engaged and forced the planes' noses to point down due to a problem with the design of the system's software. Pilots were unable to regain control of the aircraft.

The system engaged because it could be activated by a single sensor reading - in both crashes, the sensors are suspected of having failed, sending erroneous data to the flight computer and, without a redundant check in place, triggering the automated system.

The automated system, the Maneuvering Characteristics Augmentation System (MCAS), was designed to compensate for the fact that the 737 Max has larger engines than previous 737 generations. The larger engines could cause the plane's nose to tip upward, leading to a stall - in that situation, MCAS could automatically point the nose downward to negate the effect of the engine size.