American Airlines Group has tacked two weeks onto the time the Boeing 737 MAX will remain off its flight schedule, as the aircraft nears the three-month month mark of global grounding after two fatal crashes.

American will scrap about 115 daily flights as it extends the MAX cancellations through Sept. 3 from Aug. 19, according to a statement from the Fort Worth, Texas-based carrier. Southwest Airlines, the biggest MAX operator, has set Aug. 5 for the MAX to resume flights, while United Continental Holdings plans for Aug. 3.

Regulators must re-certify the plane before commercial flights can resume, but say there’s no timeline for when that will happen.

Boeing is finalizing a software fix for a flight-control system malfunction linked to the accidents involving Lion Air and Ethiopian Airlines, as well as proposed new pilot training. A combined 346 people were killed in the crashes five months apart.

American “remains confident that impending software updates to the Boeing 737 MAX, along with the new training elements Boeing is developing in coordination with our union partners, will lead to re-certification of the aircraft soon,”‘ the statement said. The planes were grounded worldwide on March 13.

Customers affected by the cancellations can be booked on other flights or can request a full refund.