Boeing CEO Dennis Muilenburg faced withering questions from senators Tuesday about two crashes of 737 Max jets and whether the company concealed information about a critical flight system.

“We have made mistakes, and we got some things wrong,” Muilenburg conceded.

Some members of the Senate Commerce Committee cut Muilenburg off when they believed he was failing to answer their questions about a key flight-control system implicated in both crashes.

Boeing successfully lobbied regulators to keep any explanation of the system, called MCAS, from pilot manuals and training. After the crashes, the company tried to blame the pilots, said Sen. Richard Blumenthal, D-Conn.

“Those pilots never had a chance,” Blumenthal said. Passengers “never had a chance. They were in flying coffins as a result of Boeing deciding that it was going to conceal MCAS from the pilots.”

Sen. Tammy Duckworth, D-Il., said Boeing “set those pilots up for failure” by not telling them how the response to a nose-down command on the Max differed from previous 737s.

“Boeing has not told the whole truth to this committee and to the families and to the people looking at this ... and these families are suffering because of it,” a visibly angry Duckworth said as she pointed to relatives of passengers who died.

Muilenburg denied that Boeing ever blamed the pilots. Several times this spring and summer he said the accidents were caused by a “chain of events,” not a single factor. The comments were widely seen as deflecting blame, including to the pilots.

Muilenburg and Boeing’s chief engineer for commercial airplanes, John Hamilton, spent about 80 minutes at the witness table.

The hearing took place exactly one year after a 737 Max crashed off the coast of Indonesia and more than seven months after a second crash in Ethiopia. In all, 346 people died. Muilenburg’s testimony was the first by a Boeing executive since the crashes. The CEO is scheduled to testify before a House committee on Wednesday.