SEATTLE — FAA Administrator Steve Dickson on Thursday told safety agency staff assessing Boeing’s revised 737 MAX flight control software that they have his full support to resist any pressure to fast track the jet’s return to the air.

The clear underlying message was that Boeing will not control the timetable for getting clearance to fly the MAX again, despite repeated declarations by the company that it expects the go-ahead by year’s end.

And on Friday, Congress added to the pressure on Boeing by demanding answers, to a series of supplementary questions based on testimony at an Oct. 30 public hearing about how the MAX was originally designed, and what and when the company knew about “potentially catastrophic” vulnerabilities.

Dickson’s message was delivered in a video distributed as a “Straight from Steve” message to Federal Aviation Administration employees on Thursday.

“I know there is a lot of pressure to return this aircraft to service quickly,” Dickson said. “But I want you to know that I want you to take the time you need, and focus solely on safety. I’ve got your back.”

“I support what you are doing to scrutinize this aircraft carefully,” he said. “I’ll support the time that you need to conduct a thorough, deliberate process for a safe return to service.”

“I am not going to sign off on this aircraft until I fly it myself and am satisfied I would put my own family on it without a second thought,” Dickson added. “The only driving force is safety and the FAA fully controls the approval process.”

The message came just three days after Boeing issued an update on progress that said it “continues to target FAA certification of the MAX flight control software updates during this quarter” and that “it is possible that the resumption of MAX deliveries to airline customers could begin in December.”

Boeing’s message was seen as an attempt to reassure investors that the MAX was still on track for a return soon, despite a rocky appearance the previous week by CEO Dennis Muilenburg in a televised Congressional hearing where House representatives brought up new evidence that Boeing missed flaws in the original design of the jet’s flight control system and questioned the company’s competence and integrity.

According to an FAA source, Dickson’s message also followed objections expressed by some technical staff when they were pressed by managers to start testing Boeing’s revised software before it was final.

In addition to the video, Dickson the same day sent a memo to Ali Bahrami, the agency’s associate administrator for aviation safety, directing that his staff should continue “to adhere to a data-driven, methodical” approach to analyzing and testing Boeing’s fix for the MAX.

“Your team should take whatever time is needed to do that work. I am committed to backing you up on all this,” Dickson wrote. “I stand with you and your team in continuing to move at the pace of safety.”

Rep. Peter DeFazio (D-Ore.), chair of the House Committee on Transportation and Infrastructure, who led the grilling of Muilenburg at the Oct. 30 hearing, on Friday sent the CEO a series of written follow-up questions.

Among other questions, DeFazio demanded to know why, immediately after the Lion Air crash, any mention of the name the flight control system that had done haywire on the crash flight was excluded from Boeing’s bulletin to airlines and from the FAA’s emergency airworthiness directive.

He also asked for an explanation of Muilenburg’s initial resistance to the grounding of the MAX in the first days after the second crash in Ethiopia and why the company felt pilots didn’t need to know about the jet’s new flight control system.

And in a question clearly based on internal Boeing engineering memos that were presented at the hearing, DeFazio also asked what the company knew after the first crash about how a malfunctioning sensor on the 737 MAX interacting with the flight control system could pose a potentially catastrophic risk.

With regard to this specific risk, DeFazio asks Muilenburg, “What new information did Boeing learn only after the October 2018 Lion Air accident, that it didn’t already know previously?” and then reiterates exactly the same question but with the March 2019 Ethiopian Airlines accident in place of the reference to Lion Air.

In pointed language, DeFazio also questioned why the aging 737 design —the 737 first flew in 1967 —is still in operation through 13 amendments to its original certification.

“When will Boeing decide the 737 has had its day and that it’s time to develop an entirely new single-aisle airplane?” DeFazio asked Muilenburg.

The continuing Congressional interrogation ensures that the pressure on Boeing will not ease, even as the FAA declares its determination to resist any pressure from Boeing or the industry.