(Reuters) - Boeing Co said on Sunday it was finalizing the development of a software upgrade and a revision of pilot training for its 737 MAX, the plane that has suffered two fatal crashes in the last five months.

FILE PHOTO: The tails of Boeing 737 MAX aircraft are seen at a Boeing production facility in Renton, Washington, U.S., March 11, 2019. REUTERS/David Ryder/File Photo

The updates are intended to address how the aircraft's flight control system - MCAS (Maneuvering Characteristics Augmentation System) - responds to erroneous sensor inputs, the planemaker said here in a statement.

A 737 MAX 8 operated by Ethiopian Airlines crashed shortly after take-off on March 10, killing all 157 on board.

Ethiopia said on Sunday the crash had “clear similarities” with a Lion Air crash in Indonesia in October, according to initial analysis of the black boxes recovered from the wreckage of the March 10 disaster.

Concern over the plane’s safety caused aviation authorities worldwide to ground the model.

Boeing has been working on a software upgrade for an anti-stall system and pilot displays on the 737 MAX, its fastest-selling jetliner, following the deadly Lion Air crash, and has said it was updating pilot training as well.

One idea for revised training is an additional 10-15 minute iPad course that would explain the new software, according to Dennis Tajer, a spokesman for the American Airlines pilot union and a 737 pilot.

However, specific new pilot training is not expected to be defined until the software fix is in place, industry sources said.

Boeing plans to release upgraded software for its 737 MAX in a week to 10 days, sources familiar with the matter said on Friday.

Boeing did not immediately return a request for comment.