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Boeing on Thursday released hundreds of emails and communications that appear to show employees criticizing the company’s troubled 737 Max jet, which was grounded after two crashes killed 346 people.

In the documents that were turned over to Congress in an investigation on the design and certification of the jets, employees also appear to talk about misleading people and complain about the aircraft's design.

In a February 2018 message, one employee says: "Would you put your family on a MAX simulator trained aircraft? I wouldn't."

In another message from May of that year, a person wrote: "I still haven't been forgiven by god for the covering up I did last year." It wasn't clear what that author was referring to. The names of the employees and others in the communications are redacted.

The internal communications also show disparaging comments about Boeing, its culture and the aircraft itself.

"This airplane is designed by clowns, who in turn are supervised by monkeys," one message in April 2017 read.

Another in March 2017 appears to show a Boeing chief technical pilot stressing to others "the importance of holding firm that there will not be any type of simulator training required" to transition from another type of 737, the NG, to the Max. "We'll go face to face with any regulator who tries to make that a requirement," the email reads.

In October 2018, a Lion Air flight crashed off the coast of Indonesia, and then in March an Ethiopian Airlines flight crashed in Ethiopia, killing everyone on both planes. A total of 346 people died in the two crashes; both planes were Boeing Max jets.

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Boeing said the internal communications were "completely unacceptable."

The company acknowledged that the emails raise questions about its interactions with the Federal Aviation Administration in connection with getting the simulators qualified, but it said the simulators are working properly and are effective.

"The qualification activities referenced in these communications occurred early in the service life of these simulators," Boeing said. It said that since then, they have been repeatedly tested and qualified by experts within and outside the company.

Rep. Peter DeFazio, D-Ore., who chairs the House Committee on Transportation and Infrastructure and is investigating the design and certification of the plane, said the newly released emails were "incredibly damning."

"They paint a deeply disturbing picture of the lengths Boeing was apparently willing to go to in order to evade scrutiny from regulators, flight crews and the flying public, even as its own employees were sounding alarms internally," DeFazio said in a statement.

DeFazio said the communications show "a coordinated effort" from the earliest days of the program to conceal critical information from regulators and the public. The emails "detail some of the earliest and most fundamental errors in the decisions that went into the fatally flawed aircraft," he said.

The FAA on Thursday said that it had reviewed the documents and that its experts found nothing that pointed to any safety risks not already identified as part of an ongoing review of proposed changes to the aircraft.

The agency also said that the specific simulator mentioned in the documents has been evaluated and qualified three times in the past six months and that "any potential safety deficiencies identified in the documents have been addressed."

"While the tone and content of some of the language contained in the documents is disappointing, the FAA remains focused on following a thorough process for returning the Boeing 737 MAX to passenger service," the FAA said.

Boeing said that the communications were sent to the FAA and Congress in December. It said they contain "provocative language" and apologized.

"These communications do not reflect the company we are and need to be, and they are completely unacceptable," Boeing said. "That said, we remain confident in the regulatory process for qualifying these simulators."

The company said it has made changes to improve its culture and was reviewing the language and sentiments expressed in the messages. It said it planned disciplinary action.

In December, Boeing announced plans to suspend production of the 737 Max airplanes until regulators determine when they can be certified and returned to service.

A week later, the company fired CEO Dennis A. Muilenburg.

The plane maker just this week changed its tack on simulator training, saying it would recommend that pilots do the training before they resume flying the 737 Max — a major shift from a position it has held long that pilots only needed computer-based training, Reuters reported.

The FAA said Thursday that it is continuing to work with international regulators to review proposed changes to the aircraft, and that it has set no time frame for when the work will be finished.