But Boeing provided no timetable for the return of the model, which is grounded around the world. The F.A.A. must first approve the new software and the training. Then, Boeing said, each 737 Max will need to be manually upgraded. Finally, Max pilots will need to receive a 30-minute training program about the software.

Even if the F.A.A. does approve the new software and training soon, regulators in other nations might move more slowly. “Certification around the world will be at the discretion of those regulators around the world, and so we can’t comment on timing,” Mr. Sinnett said.

Boeing stressed that no final conclusions have been made about what caused the crashes of Lion Air Flight 610 in Indonesia in October and Ethiopian Airlines Flight 302 this month. Investigations into both crashes are continuing, but preliminary flight data and other evidence have suggested similarities between the two accidents. Investigators are examining whether the anti-stall system may have been partly to blame.

In his prepared remarks, Mr. Sinnett seemed to acknowledge that, based on the available information, there appeared to be a link between the new anti-stall software on the Max, known as MCAS, and the crashes.

“The rigor and thoroughness of the design and testing that went into the Max gives us complete confidence that the changes we’re making will address any of these accidents,” he said.

At the same time, Mr. Sinnett said that Boeing had faith in its design and engineering.

“The 737 is a safe airplane,” he said. “The 737 family is a safe airplane family. And the 737 Max builds on that tremendous history of safety.”