US aviation regulators expect to receive Boeing’s proposed software fix for the grounded 737 Max as soon as next week and will then begin a review that will include test flights and input from a technical advisory board. “We will not allow the 737 Max to fly in the US unless it is absolutely safe to do so,” Daniel Elwell, acting administrator of the Federal Aviation Administration, told policymakers on Wednesday without offering an estimate for how long the review would take, according to Bloomberg. A technical advisory board named by the agency will provide a “third set of eyes”, and its recommendations will directly affect the timing of the grounded Max’s return to service, Mr Elwell said at a hearing in Washington. Boeing is also working on a service bulletin describing the flight control system revisions, Mr Elwell told the House aviation subcommittee at a hearing on the status of Boeing’s best-selling jet, which has been grounded since March after two crashes in a five-month span. The FAA has come under fire for approving a feature known as the Maneuvering Characteristics Augmentation System, or MCAS, and for giving the plane maker too much authority to oversee itself. After a sensor on 737 Max jets in Indonesia and Ethiopia malfunctioned, MCAS continually pushed down the aircraft nose until pilots lost control. Boeing is redesigning the system to make it less prone to operate in error. Sensor Failure Policymakers grilled Mr Elwell during the hearing, quizzing him about the certification process that allowed the plane to fly. His counterpart at the National Transportation Safety Board also appeared at the hearing. Transportation and Infrastructure Committee chairman Peter DeFazio complained about the pace of receiving records. “Boeing has yet to provide a single document,” he said. “I’m hoping they will provide the documents we’ve requested voluntarily and in the not too distant future.” The company and committee investigators are in talks about how to protect proprietary information contained in records, Mr DeFazio said after the hearing. Boeing is “fully committed to providing the committee with all of the information needed on this issue, and we have already answered many questions and provided materials requested”, said spokesman Charles Bickers. As soon as there are assurances that protections are in place, the company will supply the records, he said. Mr DeFazio said he was disappointed that a single sensor’s failure had led to the crashes. “We shouldn’t have to be here today,” he said. Mr Elwell said the agency was directly involved in approving the flight-control system, participating in a test flight of the system that drove down the nose in the two accidents. The FAA’s acting chief criticized Boeing for not disclosing to the FAA or to airlines for more than a year that a 737 Max display supposed to show whether a sensor was malfunctioning wasn’t working. “I think that’s an issue, sir,’’ Mr Elwell said under questioning by Mr DeFazio. “It shouldn’t take a year for us to find out.’’ While Mr Elwood expressed frustration with Boeing’s tardy disclosure, he said the so-called angle-of-attack sensor disagree light was “advisory” on the 737 and useful for maintenance teams - but wouldn’t have made a difference in either crash. The alert lights up when twin vanes that measure a plane’s nose against the air stream provide divergent readings to flight control computers. Mr DeFazio said the committee is still in the early stages of its review of how the plane was certified by FAA. But the tragedies are shocking, including for families of victims, he said. “They deserve answers and accountability, as does the general flying public,” he said. Republican representative Sam Graves urged caution before blaming Boeing for the accidents. In his opening statement, he listed what he called multiple errors by pilots and airline maintenance workers in the accidents that he said should be considered along with Boeing’s design. “To focus on one single factor misses the forest for the trees," he said. The FAA is hosting a meeting of foreign aviation regulators on May 23 in the Dallas-Fort Worth area and Mr Elwell said part of the purpose was to repair what he called a perception that there is a “crisis of confidence’’ in the agency’s leadership. Because so many nations grounded the 737 Max in March before FAA felt it had enough data to do so, Mr Elwell said the aviation system wasn’t as collaborative as it had historically been. The FAA plans at the meeting to discuss what it knows about the efforts to fix the plane and the steps it plans to take before approving it for flight. Despite Boeing's woes US fliers still consider ticket prices the most important factor when choosing a flight, according to a Reuters/Ipsos poll, suggesting the fatal Max crashes have had little impact on consumer sentiment. In the public opinion poll released May 15, only about half of US adults say they are familiar with the aircrafyt crashes in Indonesia and Ethiopia that together killed 346 people, and only 43 per cent could identify the Boeing 737 Max as the aircraft involved. Most importantly for Boeing in the wake of the crashes, only 3 per cent said that aeroplane maker or model number was most important to them when buying a plane ticket. In contrast, 57 per cent said ticket price was most important. The poll has a credibility interval, a measure of precision, of 3 percentage points, according to Reuters. The NTSB is assisting Ethiopian and Indonesian authorities in their investigations of the two crashes, NTSB chairman Robert Sumwalt testified. The 737 Max, Boeing’s best-selling aircraft, was grounded on March 13 after it became clear the two accidents had similarities. MCAS was added to the 737 Max to make it less likely to enter an aerodynamic stall. It automatically commands a relatively modest dive if it senses a plane’s nose has gotten too high. In the accidents, it repeatedly pushed down the nose despite efforts by the pilots to counter it. The crashes killed 346 people. At a separate hearing Wednesday, senators pressed the nominee to become FAA administrator, Stephen Dickson, on whether the agency needs to change procedures that led to certification of the 737 Max. Several policymakers focused on the use of aircraft manufacturers’ employees to sign off on designs, Bloomberg reported. “Whatever corrective actions need to be taken or process changes need to be put in place, I can guarantee you that those will be accomplished," Mr Dickson said. He also said it’s “very important not to jump to conclusions”. “Working with the private sector with the proper controls and protocols is going to allow the regulator to be much more effective and add a lot more safety value that just throwing extra resources at it," Mr Dickson said.