A FIX to the anti-stall system suspected of causing the crash of a Boeing 737 MAX 8 jet that killed 189 people in Indonesia is ready, industry sources said on Saturday, as the company tries to avoid a lengthy grounding of its planes.

Boeing was due to present the patch to officials and pilots of US airlines – American, Southwest and United – in Renton, Washington state, where the plane is assembled, other sources said.

“Boeing has already finalised the necessary corrective measures for the MAX,” an aviation sector source told AFP on condition of anonymity.

The Federal Aviation Administration (FAA) will receive the patch “early next week”, a government source added.

Asked how long the certification process could take after the patch is in the hands of the authorities, this source said that nothing has been decided yet.

The FAA declined to comment.

The Lion Air crash in Indonesia last October and another accident this month involving an Ethiopian Airlines jet, which killed 346 people between them, have raised major concerns about the safety certification of the 737 MAX 8 model.

The Ethiopian Airlines crash on March 10 led to the global grounding of 737 MAX planes.

Although it will take months to determine the exact cause of both crashes, investigators in the Lion case have honed in on the Maneuvering Characteristics Augmentation System automated anti-stalling system designed to point the nose of the plane downward if it is in danger of stalling, or losing lift.

American Airlines and Southwest pilots were set to test simulators with the updates on Saturday, according to the sources.

Boeing neither confirmed nor denied the information.

The FAA had given until April for Boeing to make the necessary changes to the critical anti-stall system, and on March 15 two anonymous industry sources said the upgrade would be ready in about 10 days.

A spokesman for United Airlines, whose fleet includes 14 of the 737 MAX 9 planes, confirmed the company’s attendance at the training session.