SHEFFIELD — If the embattled Boeing 737 Max jetliners return to the skies, Michael Stumo wants to ensure they're safe.

More than three months after his daughter was killed in a crash of one of the planes — the second in five months — Stumo has been in Washington to listen, and eventually testify, about the fatally flawed jetliners.

And he is hopeful that lawmakers and regulators will be thorough in their scrutiny of the jets before allowing them to resume service.

"Most people are agreeing with what we're saying here," said Stumo, whose daughter, Samya Stumo, was killed in the Ethiopian Airlines crash on March 10. "You don't rely on the pilots to catch a broken design and be the last catch before plummeting to the ground. The hearing today did not have the deflection of pilot error by some, saying 'Oh, it's those untrained foreign pilots. We're safe. There's nothing to see here — please move along.'"

Samya Stumo, a Sheffield native working for a global health nonprofit, was on her way to Kenya and Uganda when the plane took a nosedive after the flight crew was stymied by the plane's computerized flight control system. The plane crashed minutes after takeoff in Ethiopia, killing all 157 passengers and crew.

In October, a Lion Air jet crashed in Indonesia, killing 189. The anti-stall flight control system, or MCAS, was a factor in both crashes, investigators say.

The Ethiopian crash set off a storm of federal investigations that includes a criminal probe by the U.S. Justice Department, as well as calls that Boeing replace its executives. And the Stumo family has filed suit in federal district court in Chicago, one of 35 filed there, according to Pamela Sakowicz Menaker, a spokeswoman for Clifford Law Offices, a Chicago firm that is handling 20 of those cases.

Attorneys claim corporate and regulatory malfeasance in rushing the Max jets to market. And it is the jet model's MCAS system that has become the focal point for aviation experts.

Amid what a pilots union boss called a "crisis of trust" stemming from design and software concerns about the jets, Samya Stumo's parents have attended a flurry of meetings on Capitol Hill this week.

Michael Stumo and Nadia Milleron also sat in on a congressional hearing Wednesday held by the House Aviation Subcommittee, one which featured pilot testimony critical of Boeing.

In a phone call from the Rayburn House Office Building, Stumo said that he and Milleron have already had 30 meetings with subcommittee members, National Transportation Safety Board officials, and the Federal Aviation Administration's acting administrator, "who assured us that there is no timeline [for clearing the planes] — 'it's safety first.'"

U.S. Rep. Peter A. DeFazio, chairman of the House panel, told the Stumo family they would be able to testify at a future hearing, Michael Stumo said.

And Stumo says that a protective subpoena could allow whistleblower testimony that could tilt the entire situation.

"We believe there are people who complained within Boeing, were ignored, then complained to the FAA," he said, adding that it appears the employees were fired by the company after their names were leaked.

"We're also asking [the panel] to have people who wrote the software testify," Stumo said.

With artificial intelligence becoming more of a factor in future software design, Stumo said, he wants to make sure software engineers have aviation expertise.

"Or do they write 'Angry Birds' software in their free time?" he said, referring to the popular video game.

A turning point came at Wednesday's hearing, when a retired pilot acclaimed for his emergency landing in 2009 of a US Airways jet on the Hudson River told the panel that the MCAS system on the Max jet was "fatally flawed and should never have been approved."

Capt. Chesley "Sully" Sullenberger also said that pilots should undergo extensive simulator training to manage the software system.

'Axe the Max'

Consumer advocate Ralph Nader entered this fray at the beginning — Samya Stumo was his grandniece. He told The Eagle of a new campaign to keep the Max planes out of the air.

He is selling "Axe the Max" pins on his website, where he accuses Boeing of profit-driven corruption.

"Boeing did not reveal, did not warn, did not train, and did not address the basic defective aerodynamic design of their plane," the page alleges. "Boeing's bosses gagged everyone that they could."

Nader also said he, Stumo and Milleron will speak at the American Museum of Tort Law in Winsted, Conn., on Saturday in a remembrance of the victims of the Ethiopian flight and of Samya Stumo's work to transform health care access around the world.

They will also talk about the effort to hold Boeing and the FAA accountable.

Stumo says he's seeing some signs that could happen.

"Despite the fact that Boeing give campaign contributions to around 300 members of Congress, especially aviation subcommittee members," he said. "But any tentative defense of Boeing ... seems to be withering as unsustainable."

Heather Bellow can be reached at or on Twitter @BE_hbellow and 413-329-6871.