The largest USA airline, which had previously canceled about 140 flights a day through December 3, upped its estimate for the impact of the groundings on third-quarter pre-tax profit to $140 million, $15 million more than a previous estimate.
American said it expects third quarter costs per passenger seat to increase 4 to 6%, year-over-year, excluding fuel and special items.
The Max accounted for virtually the entire drop in Boeing shipments.
The airline said Wednesday that it expects to slowly bring the plane back into its schedule starting January 16.
The FAA has signaled the return of the plane could occur in stages by country in light of a lack of consensus among regulators.
The FAA responded Wednesday by saying the agency is "following a thorough process, not a prescribed timeline, for returning the Boeing 737 Max to passenger service". "We are in continuous contact with the Federal Aviation Administration (FAA) and the Department of Transportation (DOT)", the airline said.
Boeing delivered just five 737 planes during the latest quarter, down from 138 in the 2018 period. United Airlines, the other U.S. airline with the plane in its fleet, has canceled flights through December 19. Boeing and its CEO, Dennis Muilenburg, had said until early October - when the fourth quarter began - that the company expected the plane to be cleared for flight in "early fourth quarter".
It did say, however, that it booked the first order for a Max since April.
The two 737 Max crashes in Ethiopia and Indonesia both involved a sensor issue, which would put the aircraft in an irreversible dive while flying. Boeing is also addressing a flaw discovered in the software architecture of the 737 MAX flight-control system that involves using and receiving input from the plane's two flight control computers rather than one.
American has 24 737 MAX planes in storage and another 76 that are scheduled for delivery, including 16 by the end of the year before Boeing cut off deliveries.
The announcement comes as Southwest Airlines are suing Boeing for loss of wages totaling $US100 million as a result of the Boeing 737 MAX grounding.