Boeing (BA) - Get Report CEO Dennis Muilenburg, testifying before the U.S. Senate Commerce Committee on Tuesday, vowed to make the 737 MAX one of the safest planes in the air.

"We've dedicated all resources necessary to ensure that the improvements to the 737 MAX are comprehensive and thoroughly tested," he said in the first of two appearances before lawmakers on Capitol Hill scheduled for this week.

"When the 737 MAX returns to service, it will be one of the safest airplanes ever to fly," Muilenburg told the Senate Committee.

Muilenburg told the committee that Boeing is "deeply sorry" for the loss of life from the pair of 737 MAX crashes from late 2018 and early 2019. He said the Chicago aerospace company "deserves this scrutiny" in the aftermath. 

"There was a Dennis Muilenburg that up until five days ago I felt was a little too cocky. I felt he was someone who was self-assured, someone who made me feel like that, maybe he felt that Boeing didn't do anything wrong. This Dennis Muilenburg seems to have really understood," said TheStreet's Jim Cramer

Muilenburg definitely struck a conciliatory tone during the hearing, repeatedly taking responsibility for the failings of the jet. 

"We have learned and are still learning from these accidents. We know we made mistakes and got some things wrong," he said. 

Boeing shares at last check were rising 1.1% in trading after dipping earlier during the executive's testimony.