The head of the Federal Aviation Administration (FAA) has told US lawmakers it knew the risks of further accidents following a Lion Air crash involving the Boeing 737 Max but did not issue a grounding order until after a second incident.

Administrator Steve Dickson made the revelation during a Congressional hearing for the House Committee on Transportation and Infrastructure, which launched an inquiry into the Max following a second crash involving an Ethiopian Airlines aircraft.

A total of 346 people died in both accidents.

Analysis following the first crash in October 2018 predicted there could be up to 15 more disasters over the lifespan of the 737 Max without changes to one of the aircraft’s systems.

Boeing designed the 737 Max with the new Manoeuvring Characteristics Augmentation System (MCAS), which was programmed to push the nose of the plane down to prevent it from stalling if a sensor detected too-high an angle on take-off.

Investigators have blamed the MCAS for both crashes, and Boeing has since admitted the sensor in the aircraft involved sent erroneous data to the system, causing it to override pilot commands and push the aircraft down.

While the FAA did issue an alert to airlines about the potential danger of the system, it did not issue the mandate to ground the aircraft until after the Ethiopian Airlines tragedy.

During the Congressional hearing, Dickson was asked whether the regulator had made a mistake, to which he replied: “Obviously the result was not satisfactory.” He later admitted the agency acted in error following further questioning.

Committee chair Peter DeFazio earlier said in his opening statement: “You can be sure this committee will continue to be aggressive in our oversight efforts to determine what went so horribly wrong and why, and we will not rest until we have enacted legislation to prevent future unairworthy airplanes from slipping through the regulatory cracks and into airline service.”

He accused the FAA of ‘rolling the dice on the safety of the travelling public’ by letting the Max continue to fly following the Lion Air crash.

The committee also revealed that it had become aware of an instance in which Boeing placed pressure on the FAA to overrule engineers’ concerns on safety-critical issues. A whistleblower said engineers had determined that an uncontained engine failure on the Max could send shrapnel through the rudder control cables, meaning pilots could likely lose control of the plane during the initial climb off the runway or during a take-off roll.

DeFazio said a single FAA manager overruled the “unanimous judgement of more than a dozen FAA safety experts”.

Chair of the Subcommittee on Aviation Rick Larson later said “the FAA must fix its credibility problem”.

The statements come after Boeing CEO Dennis Muilenburg was told by lawmakers they believed the manufacturer had put profit before safety on the 737Max programme, highlighting concerns that the company had engaged in “a pattern of deliberate concealment” during the certification process.

Boeing is making changes to the Max’s MCAS, but there is no solid estimate of when the aircraft will fly again. However, American Airlines has said it believes scheduled commercial flights will begin in March based on guidance from the FAA.

Dickson said the 737 Max will need to pass 12 tests before the FAA can clear it to return to service, adding this is unlikely to happen by the end of this year as hoped by Boeing.

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