Dennis Muilenberg spoke out in a video message on Monday night (March 18) following two fatal crashes involving 737 MAX aircraft in the past five months.

Lion Air flight JT 610 came down in the Java Sea last October shortly after taking off from Jakarta. All 189 people on board were killed.

This was followed by Ethiopian Airlines flight ET 302, which crashed on March 10 shortly after taking off from Addis Ababa. All 157 people on board died.

Data from the Lion Air flight recorder suggested a new anti-stall system forced the aircraft’s nose down, which the pilots were unable to override.

Ethiopia’s transport minister Dagmawit Moges said data from the Ethiopian Airlines flight recorder showed “clear similarities” with the Lion Air crash.

All 371 Boeing 737 MAX aircraft currently in service have now been grounded. In Europe, Tui operates 15, Norwegian 18 and Icelandair three.

Muilenberg said his and everyone at Boeing’s “deepest sympathies” went out to those affected by both the Lion Air and Ethiopian Airlines crashes.

He added that work to understand more about both crashes, particularly the more recent Ethiopian Airlines disaster, was progressing “thoroughly and rapidly”.

“Soon, we’ll release a software update and related pilot training for the 737 MAX that will address concerns discovered in the aftermath of the Lion Air Flight 610 accident,” said Muilenburg.

Boeing previously said its software update would concern the 737 MAX’s Manoeuvering Characteristics Augmentation System (MCAS), as well as how MCAS data is displayed to pilots.

The MCAS is an under-the-hood feature of the 737 MAX, designed to address stalls – situations when the angle at which an aircraft is flying becomes too steep.

A pilot would normally recover a stall by pushing the aircraft’s nose down manually. However, the MCAS on the 737 MAX is designed to do this automatically with no input from a pilot.

Following the Lion Air crash, Boeing said it had detected "erroneous input” from an angle of attack sensor, which helps the aircraft judge whether its nose is correctly positioned.

Besides the software update, the aircraft manufacturer has said it is also working on updates to its operation manuals and crew training.

Muilenburg added: “Based on facts from the Lion Air Flight 610 accident and emerging data as it becomes available from the Ethiopian Airlines Flight 302 accident, we’re taking actions to fully ensure the safety of the 737 MAX.

“We also understand and regret the challenges for our customers and the flying public caused by the fleet’s grounding.”