Boeing says it regrets concerns caused by leaked messages from a former employee about issues with the 737 Max automated safety system as it was being certified in 2016.

A technical pilot involved in the development of training and manuals exchanged instant messages highlighting unexpected trouble during tests.

This came almost two years before a flight control system on the new generation aircraft contributed to the crash of a Lion Air 737 Max in Indonesia killing all 189 people on board.

A 737 Max flown by Ethiopian Airlines went down in March this year with the loss of 157 lives. All Max aircraft have been grounded since.

The latest disclosure prompted Business Travel Coalition chairman Kevin Mitchell to call for Boeing CEO Dennis Muilenburg and other members of the leadership team to be replaced.

Mitchell said: “The text messages disclosed last week, apparently, after months in Mr Muilenburg’s possession, are deeply troubling both because they were hidden from the Federal Aviation Administration and Congress and because of the damning content they contained.”

Investigators at the US Federal Aviation Administration are focusing on whether the Manoeuvring Characteristics Augmentation System (MCAS) flight control system on the 737 Max caused or contributed to both crashes.

Boeing said yesterday: “We understand and regret the concern caused by the release Friday of a Nov. 15, 2016 instant message involving a former Boeing employee, Mark Forkner, a technical pilot. And we especially regret the difficulties that the release of this document has presented for the US Federal Aviation Administration and other regulators.

“It is unfortunate that this document, which was provided early this year to [US] government investigators, could not be released in a manner that would have allowed for meaningful explanation.

“While we have not been able to speak to Mr Forkner directly about his understanding of the document, he has stated through his attorney that his comments reflected a reaction to a simulator program that was not functioning properly, and that was still undergoing testing.

“We are continuing to investigate the circumstances of this exchange, and are committed to identifying all the available facts relating to it, and to sharing those facts with the appropriate investigating and regulatory authorities.”

The manufacturer added: “We are deeply saddened and have been humbled by these accidents, and are fully committed to learning from them.

“We have developed improvements to the 737 Max that will ensure that accidents like these can never happen again, and are committed to continuing to work closely with the FAA and global regulators to ensure the MAX’s safe return to service.”