The boss of Boeing faced accusations from US lawmakers that the company put profits before safety as it rushed to gain clearance for its 737 Max to fly.

Chief executive Dennis Muilenburg admitted the manufacturer had made “mistakes” when questioned at a senate hearing in Washington.

He was confronted by relatives of victims of two 737 Max crashes in Indonesia and Ethiopia which killed a total of 346 people and led to the firm’s best selling aircraft being grounded in March.

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Lawmakers accused Boeing of being aware of problems in the automated flight control system in the 737 Max 8, known as MCAS, which has been identified as a factor in both accidents.

Senator Roger Wicker said messages between Boeing staff during certification in 2016 that raised issues in the MCAS test system betrayed “a disturbing level of casualness and flippancy”.

Senator Richard Blumenthal said Boeing had rushed the approval process and engaged in a “pattern of deliberate concealment”.

He suggested that pilots had been misled and Boeing had, in effect, designed a ‘flying coffin’.

Boeing provided the messages to the committee ahead of the testimony.

Muilenburg said he had learned the details of the exchange recently could not elaborate on the communication.

Senators also criticised the regulatory process, saying there was excessive “cosiness” between Boeing and safety officials at the US Federal Aviation Administration.

Blumenthal described the US certification process as “absolutely broken”.

Muilenburg said the firm supported “strong oversight” but declined to support increasing the authority of the FAA, which has been criticised for delegating too much of its oversight to company officials.

Muilenburg said safety is enhanced by tapping industry technical expertise.

The company also disputed the characterisation of its relationship with regulators as “cosy”.

“It’s not a cosy relationship. It’s a professional relationship,” said Boeing’s chief engineer John Hamilton.

Boeing has said it is fixing software and has overhauled its review procedures since the grounding of the 737 Max in the wake of the deadly Lion Air and Ethiopian Airlines crashes.

But senators said the continued delays in re-certification cast serious doubt on the initial approval.

They criticised Boeing for not sharing more information about the MCAS system with regulators or pilots, despite its power to control the flight path of the new generation aircraft.

Senator Maria Cantwell said the crashes should spur broader scrutiny of automated systems, which are becoming more common – not just in aircraft but also in cars and other forms of transportation.

Muilenburg said: “We can and must do better. We have been challenged and changed by these accidents. We’ve made mistakes and we got some things wrong.

“We’re improving and we’re learning and we are continuing to learn.”

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