(CNN) - The acting head of the Federal Aviation Administration raised concerns Wednesday both with the actions of pilots whose 737 Max jets crashed, and the decisions of his agency and planemaker Boeing.
Acting administrator Daniel Elwell delivered his most pointed assessment to date in comments before Congress of the Lion Air pilots whose plane crashed last October. They did not identify and use an emergency checklist that could have disabled the automated system -- the Maneuvering Characteristics Augmentation System, or MCAS -- that pushed the airplane downward, he said.
But, he acknowledged, Boeing should have included more information about that faulty stabilization system -- new for the 737 Max -- in its pilots manual. The existence of the system was not revealed in the manual prior to that crash, leaving pilots in the dark.
"As a pilot, when I first heard about this, I thought there should have been more text in the manual about MCAS," Elwell, a former military and commercial pilot, said.
Elwell took questions from House lawmakers about the certification of the 737 Max, its process for allowing planemakers to sign off on certification decisions, why MCAS was not subject to a more rigorous review, and how FAA will go about evaluating the airplane's safety and returning it to the skies.
The 737 Max 8 and 9 were grounded worldwide after a second crash in Ethiopia two months ago that investigators have described as appearing similar to the Lion Air flight, which ended with a plunge into the Java Sea. Between the two crashes, 346 people died.
Elwell said FAA expects to receive a Boeing software update and pilot training plan to fix the problem "in the next week or so." The FAA has scheduled a May 23 meeting with its worldwide counterparts.
He also promised to learn lessons from multiple ongoing reviews. There's an ongoing criminal probe, an advisory panel set up to help review Boeing's proposed fixes, a blue ribbon commission to review FAA's certification practices, and an international collaborative review into the Max.
The Trump administration's nominee to lead the FAA, Stephen Dickson, testified simultaneously at a separate hearing on the Senate side of the Capitol. In his first public comments on the Max, Dickson pledged to "be the captain of the ship" and oversee improvements to FAA practices.
Since Elwell's last testimony before Congress, news reports have revealed how the FAA certification process allowed Boeing officials with authority delegated from the FAA to certify their company's own work.
Elwell identified shortcomings of his own agency, including the assignment of less stringent review standards for the MCAS system than for items deemed critical to the aircraft's safety.
"I didn't make that designation, but it seems to me yes, it is" critical, he said.
He also expressed "concern" that Boeing did not notify regulators or customers for about a year after identifying a cockpit alert light that should have illuminated when the angle of attack sensors drew divergent readings. The alert, which could have given the pilots additional information, was supposed to be standard on all Max planes but was only operational on those airlines that had paid for an optional upgrade. Preliminary crash reports revealed bad data flowing into the MCAS system, triggering the automatic lowering of the aircrafts' noses, and ultimately the fatal dives.
But he also drew from investigators' public preliminary reports to find fault with how the pilots handled the malfunctions.
The Ethiopian pilots, he said, "didn't adhere to the emergency (Airworthiness Directive) that we put out" after the Lion Air crash.
Although the pilots did cut power to the MCAS system, "they never controlled their airspeed," and finding the manual process outlined in the checklist difficult, ultimately turned the automated system back on.
It is not clear that the pilots would have had enough altitude to correct the issue, aviation experts, including pilot union officials, have told CNN.
The emergency flight procedure specified in that directive has not been substantially updated since the 1960s and is now under FAA review, CNN recently reported.
Ahead of Elwell's testimony, the Allied Pilots Association, a major union, released audio of a conversation its leadership had with Boeing officials last November, after the Lion Air crash.
"We're the last line of defense to being in that smoking hole and we need the knowledge," one unidentified pilot is heard saying on the tape, which was first reported by The New York Times.
Captain Daniel F. Carey, a union official, said in a statement the audio shows "Boeing did not treat the 737 Max 8 situation like the emergency it was."
Boeing responded in a statement on Wednesday saying it is "focused on working with pilots, airlines and global regulators to certify the updates on the Max and provide additional training and education to safely return the planes to flight."
This post has been updated with additional developments Wednesday.