A separate major mistake involved software controlling thrusters that help to angle the craft properly to avoid damaging the heat shield that protects the capsule, and any astronauts inside, during re-entry. Engineers detected and were able to correct that software glitch from the ground in time to ensure that what would be the crew's portion of the capsule safely separated from the rest of the spacecraft before re-entry.

After the botched mission, Boeing's board -- already frustrated by the MAX crisis -- ousted then-CEO Dennis Muilenburg and replaced him with Mr. Calhoun. Mr. Muilenburg had once boasted that Boeing would be first to put humans on Mars. The company booked a $410 million charge to account for the Starliner launch's redo.

Current and former government and industry officials blame the spotty testing on cost-cutting and inadequate staff. Boeing was years late delivering the Starliner under a fixed-price contract that created incentives for managers to keep a lid on testing and personnel costs. In addition, the company was vying with SpaceX to get the first astronauts into orbit on a commercially owned and operated capsule. Mr. Musk's team handily won that race with launches in May and November. Another closely held competitor, run by Amazon.com Inc.'s founder Jeff Bezos, is also taking aim at Boeing's legacy of space leadership.

A NASA spokesman said "deadline pressures and cost cutting were not identified" by a joint NASA-Boeing review team as causes of the Starliner's problems.

Patricia Sanders, chairwoman of NASA's independent safety-advisory committee, said the signs point to basic lapses in Boeing's engineering discipline. "It's possible that there was some complacency that set in," she said, adding that Boeing leaders now seem to realize they have to change course. "There is a sense that Boeing overall has woken up."

Boeing, under pressure from government officials, has added software engineers to the Starliner team, industry officials said. A newly appointed program manager, John Vollmer, is known for his ability to execute on difficult programs, according to people familiar with the matter, and is prodding Starliner engineers to more thoroughly test software and address problems identified by the flurry of post-failure reviews.

A Boeing spokesman said the company is poised to begin full-mission simulation testing as soon as next month after making software changes recommended by an independent review ordered by NASA.

Kathy Lueders, NASA's head of human space exploration, has singled out the agency's overreliance on Boeing's traditional engineering expertise as the crux of the Starliner's failures. Rather than reflexively trusting Boeing's technical judgment in most matters -- as NASA had long done -- "we do need to change our assumptions as to how we are working together" to ensure Boeing avoids mistakes, she told reporters in July. The upshot was tighter restrictions on Boeing's engineering decisions.

NASA has ramped up its own staffing and oversight of Boeing, acknowledging it probably paid too much attention to keeping tabs on Mr. Musk's company, until recent years viewed by career agency officials as an outsider and upstart.

In addition, government watchdogs have criticized Boeing for persistently missing deadlines and busting budgets as the prime contractor for the nation's premier deep-space rocket, the mammoth Space Launch System. Every major component of the heavy-lift booster has experienced technical challenges and performance issues, according to a March 2020 report from NASA's inspector general, resulting in at least $2 billion in recent cost increases. Additional delays could add another $8 billion.

After nearly a decade of development, it still isn't slated to fly until November at the earliest. A long-awaited test intended to fire up all four main engines for the first time is scheduled for Saturday.

As its engineers work to vet the Starliner's software, the Boeing spokesman said, the company will perform a full end-to-end test of the capsule's mission, from prelaunch to landing. For the next blastoff, people familiar with the matter said, Boeing isn't planning to hold a flashy party.

Write to Andy Pasztor at andy.pasztor@wsj.com and Andrew Tangel at Andrew.Tangel@wsj.com

(END) Dow Jones Newswires

01-16-21 0014ET