The union representing the Federal Aviation Administration engineers overseeing Boeing’s redesign of the grounded 737 Max says the government’s proposed fixes to the plane don’t go far enough. The National Air Traffic Controllers Association, which represents FAA engineers who review and sign off on aircraft certification, said in comments filed on Monday that the Max should have to adhere to tougher standards on cockpit alerts. Because the plane was adapted from earlier versions, portions of its design weren’t required to meet the latest safety requirements. The union said that the proposed fixes to the jetliner are extensive and the most current regulations should apply. The comments are significant because they suggest that at least some of the FAA’s own technical staff don’t agree on the extensive proposed revisions to the plane. A whistle-blower at Boeing separately urged regulators to add additional protections to the plane. The FAA has proposed multiple changes to the aircraft following the crashes that killed 346 people before allowing it to carry passengers again. Among the changes: The system that was driving the jet’s nose down in both accidents would no longer activate repeatedly and various steps were taken to minimise the chances it would malfunction. The agency is also proposing to require extensive additional revisions to the plane, such as an improved flight-computer system to improve the system’s redundancy. Before the FAA can mandate the fixes, it must sift through the comments, which totaled more than 200 as of Monday afternoon. The deadline for comments is the end of the day. The filings range from frightened consumers who say they won’t fly on a Max to highly technical white papers by engineers. The NATCA comments don’t say whether individual engineers had objected to the FAA’s preliminary approval of Boeing’s redesign. The agency’s rank-and-file engineering staff have at times charged that they were unfairly overruled by managers, according to various reports after the crashes, including one from House Democrats released September 16. There’s also no indication how expensive and time consuming it would be to follow the union’s recommendation. The proposed redesigns of the plane took more than a year to reach this stage. The NATCA comments include five separate recommendations. They range from relatively minor changes in emergency procedures to a call for what appear to be more extensive revisions to the plane’s cockpit alerting system. Despite proposed changes to the plane, it would still be subject to erroneous warnings from a single sensor, the union said. “This design does not comply” with FAA regulations and could lead to pilot confusion, it said. The US National Transportation Safety Board last week said the FAA’s proposals were consistent with its recommendations on the plane issued last year, while family and friends of crash victims urged wholesale changes before the plane returns. The Air Line Pilots Association, which represents more than 60,000 flight crew members in North America, proposed several changes to the FAA plan, such as giving pilots the ability to disable the loud thumping warning that occurs when a plane is about to enter an aerodynamic stall. Boeing said in a statement that it wouldn’t respond to the comments on the FAA’s proposed fixes. The FAA said in a statement that it would “consider all comments.” Boeing closed down 2.97 per cent to $156.35 in New York amid broad market declines. The shares tumbled a little more than 50 per cent this year through September 18, the biggest drop on the Dow Jones Industrial Average. Curtis Ewbank, a whistle-blower who has previously raised concerns about the plane’s design with congressional investigators, said in comments filed with the FAA that a proposal to mandate fixes to the jetliner didn’t address multiple hazards identified in the two fatal Max accidents and earlier incidents. “Clearly more actions are required to revise FAA processes so that it accurately assesses airplane design and regulates in the public interest,” Mr Ewbank said in the comments, posted on the Regulations.gov website. Mr Ewbank said the FAA and Boeing should do more to prohibit faulty readings from the sensor implicated in both crashes and improve the plane’s warning systems. In addition, the agency should do a broader review of how pilots react to emergencies and do a more thorough redesign of the flight-control system, he said. The FAA and the European Aviation Safety Agency are also planning to require Boeing to adopt longer-term fixes after the aircraft’s return, some of which are similar to what Mr Ewbank is seeking. A consumer group that advocates for airline passengers, Travelers United, said it supported the plane’s return. “After this thorough and unprecedented review of the plane’s safety, it is time to get the 737 Max planes in the air serving the flying public where they can enhance travel options for consumers and reduce carbon emissions and fuel burn,” wrote the group’s president, Charles Leocha. A retired Boeing engineer who said he worked on the 737 decades ago called on the company to release more technical information about the design of the system implicated in the crashes. Robert Bogash, who said he has also been involved in accident investigations, said simpler changes to the plane, such as limiting its weight and balance, could accomplish the same thing as the automated system involved in the two crashes with less risk. “Personally, none of us want another 737 accident – we have devoted our careers to that remarkable airplane – and my suggestions and comments are aimed at ensuring that the outcome of this prolonged grounding are as effective as possible,” Mr Bogash said.