With virtually every day that has passed since the crash of Ethiopian Airlines Flight 302, which killed a hundred and fifty-seven people, more disturbing news has emerged. On Sunday, a spokesperson for Ethiopia’s ministry of transport said that the black box that was recovered from the wreckage of Flight 302 indicated that “clear similarities were noted between Ethiopian Airlines Flight 302 and Indonesian Lion Air Flight 610,” which crashed last October, killing a hundred and eighty-nine people.

The plane involved in the Lion Air tragedy was also a Boeing 737 Max 8, and investigators suspect that the cause of that crash was a malfunctioning automated-flight-control feature, which caused the aircraft’s nose to dip repeatedly during its initial ascent out of the airport in Jakarta. The automated-flight-control feature on the 737 Max, which is called a Maneuvering Characteristics Augmentation System (MCAS), was designed to prevent a high-speed stall. It works by tilting part of the horizontal stabilizer in the tail of the plane, and investigators at the Ethiopian crash site have found physical evidence that this part of the plane was, indeed, configured to dive.

Radar data has indicated that both planes jerked up and down in erratic fashion after takeoff. The captain of the Ethiopian Airlines flight reported a “flight control” problem to the air-traffic control tower. Data from the black box of the Lion Air plane showed that its pilots repeatedly pulled back on the control yoke to try to disengage the MCAS and level the flight path of the plane. “The pilots fought continuously until the end of the flight,” an official from the Indonesian National Transportation Safety Committee said in November, after the plane’s black box was recovered.

This is all frightening enough, and it raises serious questions about why Boeing didn’t tell airlines and pilots much more about the MCAS—in particular, how to disengage it in an emergency—before the 737 Max was put into service, in 2017. Boeing has delivered three hundred and seventy-six of these planes to airlines around the world. Practically all of them have now been grounded out of safety concerns.

Boeing has promised a software fix to address some of the potential problems created by the MCAS. That’s too little, too late, of course, and it doesn’t address the even larger issue of how the 737 Max was allowed to fly in the first place. On Sunday, the Seattle Times, the home-town newspaper of Boeing’s commercial division, published the results of a lengthy investigation into the federal certification of the 737 Max. It found that the F.A.A. outsourced key elements of the certification process to Boeing itself, and that Boeing’s safety analysis of the new plane contained some serious flaws, including several relating to the MCAS.

The Boeing analysis “understated the power of the new flight control system,” the Seattle Times article said. “When the planes later entered service, MCAS was capable of moving the tail more than four times farther than was stated in the initial safety analysis document.” The Boeing analysis also “failed to account for how the system could reset itself each time a pilot responded, thereby missing the potential impact of the system repeatedly pushing the airplane’s nose downward.”

In the case of the Lion Air flight, investigators suspect the MCAS was reacting to faulty data gathered from a single flight sensor mounted on the fuselage. According to the Seattle Times article, the Boeing analysis assessed the failure of the MCAS system as “as one level below ‘catastrophic.’ But even that ‘hazardous’ danger level should have precluded activation of the system based on input from a single sensor—and yet that’s how it was designed.”

How can a manufacturer of something as complex and potentially dangerous as a passenger jet be allowed to play such a large role in deciding whether its product is safe? It turns out that the F.A.A., with congressional approval, has “over the years delegated increasing authority to Boeing to take on more of the work of certifying the safety of its own airplanes,” the Seattle Times said. In the case of the 737 Max, which is a longer and more fuel-efficient version of previous 737s, Boeing was particularly eager to get the plane into service quickly, so it could compete with Airbus’s new A320neo.

Early on, employees of the F.A.A. and Boeing decided how to divide up the certification work. But, partway through the process, a former F.A.A. safety engineer told the Seattle Times, “we were asked by management to re-evaluate what would be delegated. Management thought we had retained too much at the FAA.” The engineer said that “there was constant pressure to re-evaluate our initial decisions,” and “even after we had reassessed it … there was continued discussion by management about delegating even more items down to the Boeing Company.”

Even the work that was retained, such as reviewing technical documents provided by Boeing, was sometimes curtailed. “There wasn’t a complete and proper review of the documents,” the former engineer added. “Review was rushed to reach certain certification dates.”

The new revelations don’t stop there. “Federal prosecutors and Department of Transportation officials are scrutinizing the development of Boeing Co.’s 737 MAX jetliners,” the Wall Street Journal reported on Monday. “A grand jury in Washington, D.C., issued a broad subpoena dated March 11 to at least one person involved in the 737 MAX’s development, seeking related documents, including correspondence, emails and other messages,” a source told the paper. (The Justice Department and Department of Transportation declined to comment on the Journal’s reporting.)

The criminal investigation began well before the crash of the Ethiopian Airlines Flight. It’s not clear yet whether it is focussing on the MCAS system, the report in the Journal said. But, that article added, “In the U.S., it is highly unusual for federal prosecutors to investigate details of regulatory approval of commercial aircraft designs, or to use a criminal probe to delve into dealings between the FAA and the largest aircraft manufacturer the agency oversees. Probes of airliner programs or alleged lapses in federal safety oversight typically are handled as civil cases, often by the DOT inspector general.”

In a statement to the Seattle Times, Boeing said that the F.A.A. “considered the final configuration and operating parameters of MCAS during MAX certification, and concluded that it met all certification and regulatory requirements.” The F.A.A., in a statement issued on Sunday, said that the “737 MAX certification program followed the FAA’s standard certification process.”

Given that two brand-new 737 Maxes have plunged to earth, befuddling their pilots and costing three hundred and forty-six people their lives, these statements are hardly reassuring. We need to know a lot more about how the F.A.A. allowed this plane to take to the air.