According to the India's ministry of the civil aviation, it has been announced that they will ground the 737- Max Boeing planes on the immediate basis.
Muilenburg added that Boeing have been working in "full co-operation" with authorities and regulators.
Boeing Chief Executive, Dennis Muilenburg, is attempting to win back the public's trust after the USA plane manufacturer's 737 MAX model was involved in two crashes within five months that left no survivors.
In the letter, Muilenburg said the company knew that lives depended on the work it did and its teams embraced that responsibility with a deep sense of commitment every day.
Under scrutiny is a new automated system in the 737 MAX model that guides the nose lower to avoid stalling, while Boeing has raised questions in the Lion Air case about whether crew used the correct procedures.
The FAA raised eyebrows last week after delaying its decision to ground Boeing's jet in USA airspace until after virtually all other aviation authorities around the world had done so.
China's Ministry of Commerce, which is in charge of the nation's trade talks with the US, didn't immediately respond to a request for comment. Similarly, Lion Air Flight 610, a 737 Max 8 delivered in August 2018, went down just after departure, moments after the pilot sought to return to the field.More news: Aaron Finch outlines Smith, Warner vision
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More details about the probe have yet to be revealed publicly but a person familiar with the investigation, on condition of anonymity, said a grand jury subpoena is now in the works.
"Boeing management has not been particularly pro-active in its response, and we think the shares are subject to downward pressure as the investigation plays out in the news", Argus analyst wrote in a note on Tuesday.
Boeing CEO Dennis Muilenburg said Monday a software update and related pilot training for the 737 MAX will be released "soon" and will address concerns discovered in the aftermath of the Lion Air crash.
Acting FAA Administrator Dan Elwell said on Wednesday in a call with reporters that he was "absolutely" confident in the certification of the Boeing 737 MAX 8.
US Federal Aviation Administration employees warned seven years ago that Boeing had too much control over safety approvals of new aircraft, prompting an investigation by Transportation Department auditors who confirmed the agency hadn't done enough to "hold Boeing accountable".
As investigations into the exact cause of the most recent crash continued over the weekend, Ethiopia's government said there was a "clear similarity" between the two incidents.
Boeing and the FAA declined to comment on that.