Boeing documents now under review by a US government committee appear to point to a "very disturbing" picture of commentary from the planemaker's employees over the grounded 737 Max aircraft.

That is according to a House of Representatives transportation infrastructure committee aide.

The documents, submitted to the committee late on Monday, discussed concerns over Boeing's commitment to safety, along with efforts by some employees to ensure the company's production plans were not diverted by regulators or others, said the aide, who spoke on condition of anonymity.

Boeing was not immediately available for comment.

The documents were submitted to the Federal Aviation Administration (FAA) on the same day Boeing announced the firing of its chief executive Dennis Muilenburg amid a crisis following its handling of the aftermath of two fatal crashes involving the best-selling 737 Max.

The 737 Max has been grounded since March. The crashes in Indonesia and Ethiopia killed 346 people, including Irishman Mick Ryan.

This latest batch of documents submitted to the FAA contained instant messages from a former Boeing senior pilot, Mark Forkner, according to a person briefed on the matter.

In October, Boeing turned over 2016 messages to the FAA between Forkner and another pilot that said he might have unintentionally misled the US regulator and raised questions about the performance of a key safety system during testing.

Boeing had earlier turned over the documents to the US Justice Department, which has an active criminal investigation underway into matters related to the 737 Max plane.

Boeing is struggling to mend relations with US and international regulators it needs to win over to get the jet back in the air.

Boeing shares, which have dropped more than 20% over the past nine months, closed down 1.3% to $333.