Boeing (BA - Get Report) CEO Dennis Muilenburg will appear before U.S. lawmakers on Tuesday to answer questions related to the embattled airplane maker's handling over the 737 MAX jet, which was involved in two fatal crashes last year. 

"We know we made mistakes and got some things wrong," Muilenburg will tell the U.S. Senate Commerce Committee, according to an advance copy of his testimony released by the Chicago-based company. "We own that, and we are fixing them. We have developed improvements to the 737 MAX to ensure that accidents like these never happen again." 

Muilenburg's trip to Capitol Hill coincides with the one-year anniversary of the first 737 MAX crash, a Lion Air jet that plunged into the Java Sea off the coast of Indonesia minutes after takeoff. Less than five months after that incident, an Ethiopian Airlines aircraft crashed under similar circumstances, prompting a global grounding of Boeing's best-selling jetliner.

The planemaker has redesigned flight-control software linked to the crashes, known as MCAS, to ensure that the system can't be activated repeatedly and that it no longer has a single point of failure. MCAS -- short for Maneuvering Characteristics Augmentation System -- was triggered by erroneous sensor readings in both crashes.

When regulators lift the flying ban on the MAX, "it will be one of the safest airplanes ever to fly," Muilenburg will say, according to the testimony.

Shares of Boeing were down about half a cent at $340.36 in premarket trading on Tuesday. The stock closed Monday up a little more than 1% at $340.88. The shares have dropped 19% since the second MAX crash.

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