American Airlines said it would extend cancelations of flights scheduled on Boeing MAX 737s until June.
That means about 90 flights a day grounded until at least June 5, as the airline seeks to offer customers more certainty for their travel plans.
American had previously announced scheduled cancelations through April 24.
"By proactively canceling these flights, we are able to provide better service to our customers with availability and re-booking options," the airline said in a release.
The software fix for the MCAS system which has been blamed in part for two crashes, is still several weeks away, Boeing and the FAA said.
The FAA grounded all 737 Max planes on March 13, and the plane maker announced it is cutting back production of the plane with no timeline on when they will be approved to fly again.
Boeing said it will reduce production by 10 planes a month.
CEO Dennis Muilenburg acknowledged a link between the Lion Air and Ethiopian Airlines crashes.
"The full details of what happened in the two accidents will be issued by the government authorities in the final reports, but, with the release of the preliminary report of the Ethiopian Airlines Flight 302 accident investigation, it’s apparent that in both flights the Maneuvering Characteristics Augmentation System, known as MCAS, activated in response to erroneous angle of attack information," he said last week.
Muilenburg said the Boeing board will establish a committee to review current company policies for its research and development operations and recommend any revisions.
