The Boeing 737 MAX will take another key step in its comeback to commercial travel on Wednesday with an American Airlines test flight for 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.

American Airlines plans an initial commercial flight on December 29.

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. But those calamities plunged the aerospace giant into a crisis that was worsened by the coronavirus and its devastating impact on commercial air travel.

Steve Dickson, the head of the Federal Aviation Administration, 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.

A principal cause of the two crashes was identified 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 FAA required Boeing to upgrade this system to address the flaw.

Families of victims of the crashes dismissed the American Airlines flight as a "media stunt," according to Clifford Law Offices, which is representing the families 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."