Europe, however, has already signed off on the end of the flight moratorium, with the continent's central regulator saying last month that the MAX could again operate commercial flights by the end of the year.
American Airlines plans to relaunch the first commercial Max flight since the grounding on December 29.
"Despite its inability to undertake revenue operations, the company continues to incur various costs with respect to these aircraft", the airline said in a regulatory filing on November 11.
Boeing has been working since March 2019 on a fix for the model's automated flight software, a process that has been delayed by lengthy crash and oversight investigations, software development and the COVID-19 pandemic. Any return to the skies has always been contingent on a fix that was approved by the FAA.
The Airworthiness Directive issued by the FAA spells out the requirements that must be met before USA carriers can resume service, including installing software enhancements, completing wire separation modifications, conducting pilot training and accomplishing thorough de-preservation activities that will ensure the airplanes are ready for service.
Aviation regulators of different countries, including India, will need to allow this aircraft to fly again before airlines of those countries can begin operating the same after carrying out the required modifications in each Max and pilot training.
Over the past 20 months, FAA employees have worked to identify and address the safety issues that played a role in the loss of Lion Air Flight 610 and Ethiopian Airlines Flight 302, a statement from the body said.
Boeing meanwhile is scrambling to keep up maintenance and find airline buyers for many of its mothballed 737 MAXs since the coronavirus downturn sapped airlines' desire to refresh fleets. In both cases, the planes crashed shortly after takeoff and were attributed to failures in the automated flight system. "The agency also will conduct the same rigorous, continued operational safety oversight of the MAX that we provide for the entire USA commercial fleet", the statement concluded. Joining many other regulators worldwide, the Directorate General of Civil Aviation (DGCA) grounded MAX aircraft in March past year.
Even with all the hurdles, resuming deliveries of the 737 MAX will open up a crucial pipeline of cash for Boeing and hundreds of parts suppliers whose finances were strained by production cuts linked to the jet's safety ban.
The House on Tuesday unanimously passed a bill to reform how the FAA certifies airplanes, while a Senate panel is to consider a similar bill on Wednesday.