The Boeing 737 MAX will take another key step in its comeback to commercial travel on Wednesday by attempting to reassure the public with a test flight by American Airlines conducted for the news media.

After being grounded for 20 months following two deadly crashes, US air safety officials in mid-November cleared the MAX to return to service following changes to the plane and pilot training protocols.

Brazilian authorities have also okayed the MAX to fly again, while European officials are expected to approve the MAX's return by the end of January 2021. China remains the main mystery as far as when it expects the MAX to fly again.

American Airlines plans an initial commercial flight on December 29.

American Airlines has scheduled its first commercial flight with the Boeing 737 MAX late this month following a lengthy grounding American Airlines has scheduled its first commercial flight with the Boeing 737 MAX late this month following a lengthy grounding Photo: AFP / Jason Redmond

The test flight Wednesday between American's headquarters in Dallas and its maintenance center in Tulsa is intended to bolster public confidence in the jet.

The MAX had been a cash cow for Boeing prior to the Lion Air and Ethiopian Airlines crashes that together claimed 346 lives. Those calamities plunged the aerospace giant into a crisis that was worsened by the coronavirus and its devastating impact on commercial air travel.

Investigations identified a principal cause of the two crashes as a faulty flight handling system that was supposed to keep the plane from stalling as it ascended but instead forced the nose of the plane downward. The Federal Aviation Administration (FAA) required Boeing to upgrade this system to address the flaw.

FAA chief Steve Dickson described the process for recertifying the jet as exhaustive. Dickson himself piloted a test flight and said last month he was "100 percent comfortable" with having his family fly in the jet.

Boeing 737 MAX takes flight after 20 months grounded following deadly crashes Boeing 737 MAX takes flight after 20 months grounded following deadly crashes Photo: AFPTV / Kacey CHERRY

Boeing also plans to establish an operations center to monitor MAX flights in real time.

But those efforts are not enough for families of victims of the crashes, who dismissed the American Airlines flight as a "media stunt," according to Clifford Law Offices, which is representing the relatives in litigation against Boeing.

"The promotional flight is arranged by the American Airlines marketing team simply because the company made the mistake of buying more MAX aircraft than almost any other airline," said Michael Stumo, whose daughter died in the Ethiopian Airlines crash.

"Passengers should avoid this aircraft because others are safer."

With 24 MAX planes in its fleet, American Airlines has the second-largest number of planes, after Southwest Airlines with 34.

Customers canceled hundreds of orders for the MAX this year, but Boeing could see a rebound in interest should the plane again win regulatory approval.

The two companies declined comment.