Federal investigators looking into the 2014 crash of Virgin Galactic LLC's experimental rocket ship are poised to highlight safety lapses during flight preparation, according to people familiar with the matter, while internal company documents and interviews with former engineers indicate that project managers were warned about separate technical shortcomings long before the accident.

Engineers over the years had complained about excessive risk and questionable flight controls, with one even urging a halt to flight tests and asking regulators to step in. Those alleged problems, however, have no apparent connection with the sequence of events that culminated in the crash, according to government and industry officials. Yet they do underscore what were nagging concerns among some engineers about inadequate safety margins and a haste to fly.

Richard Branson's Virgin Galactic has made various design and production line changes since the crash, according to people familiar with the matter.

At a public meeting Tuesday, the National Transportation Safety Board is expected to highlight training weaknesses and inadequate crew coordination as part of its likely determination that pilot error led to the high-profile crash of a vehicle being developed by Virgin Galactic, according to the people familiar with the matter. A test pilot died in the crash of SpaceShip Two last October, which sent shock waves through the nascent space-tourism industry.

The safety board's staff, these people said, also has raised questions about design criteria and manufacturing standards, as well as the Federal Aviation Administration's limited oversight authority.

Closely held Virgin Galactic's experience—after investing more than $400 million in the rocket-powered plane over nearly a decade—highlights the technical and management challenges of making the transition from prototype vehicles to production models intended to routinely carry paying passengers to the edge of the atmosphere.

Six months prior to the accident, a flight-control expert and veteran engineer brought in to vet the system urged high-level project managers that SpaceShip Two "be grounded until such time that upgrades are made to comply with FAA…requirements that would head off a potential catastrophic event," according to a company test report reviewed by The Wall Street Journal. His concerns aren't apparently connected to what investigators believe led to the accident.

Company officials declined all comment on the safety board's focus or findings. But in an email Monday, Virgin Galactic said an enhanced engineering and safety team has "gone back over all the designs and we have every confidence that we have left no analysis undone."

The official report, slated to be completed at Tuesday's session, according to these people, also is expected examine Virgin Galactic's past reliance on partner Scaled Composites, a Northrop Grumman Corp. unit renowned for developing one-of-a-kind experimental vehicles flown only by test pilots. In this case, Scaled had the lead in building and testing a spaceplane intended to carry the general public. A new vehicle with safety enhancements could start ground tests later this year, but commercial operations are now likely delayed until at least 2017.

A spokesman for Northrop Grumman declined to comment.

In October, while SpaceShip Two was breaking the sound barrier some 10 miles above the Earth, a movable tail surface designed to safely control the craft for descent deployed prematurely, breaking the vehicle apart. Government investigators have determined that co-pilot Michael Alsbury, who died, manually unlocked the critical section at the wrong time, without receiving any command or verbally indicating his intentions as typically required.

Today, a unit of Virgin Galactic, which has Abu Dhabi's Aabar Investments as an investor, is in charge of all manufacturing and testing. In earlier years production was overseen by an entity jointly owned by Scaled Composites and Virgin Galactic. People who worked for the joint venture, known as the Spaceship Company, or TSC, argued among themselves over safety standards, according to several former engineers.

In the email, Virgin Galactic said it works hard to listen to employees "express their opinions on the vehicle," and relies on senior management "to make the right decisions."

As part of efforts to accelerate output in the summer of 2013, Joe Brennan, TSC's director of operations, sought a way to alleviate what he called "concerns and hesitancies" of various engineers to sign off on certain parts, according to a memo reviewed by the Journal. Engineers believed there were safety problems with some parts already in use on an existing prototype, and were uncomfortable vouching for their safety on a second craft, several former engineers said.

Management directed them to sign off on building those parts, though without blessing them for flight, according to the memo.

Mr. Brennan's memo in August of 2013 described a novel redefinition of the approval process, allowing engineers to approve parts for production but not use in the air. "Our tolerance of risk for production is not the same as our tolerance for risk" when it comes to flight, the memo said. It added that a signoff "does not imply that the part or assembly design has been confirmed to meet performance requirements."

Virgin Galactic said in Monday's email that the practice "is certainly common in the aerospace industry" and "we accepted the risk of parts needing to be reworked while the final touches were put on the engineering analysis," adding it was "a risk in schedule, not in flight safety."

Such procedural changes, which apparently aren't connected to the crash, are occasionally used on large-scale aerospace projects to accelerate work amid pressing production deadlines. But the move illustrated the tension between the spacecraft's experimental roots and the need to come up with a production passenger vehicle design incorporating higher reliability for essential safety systems.

The analyses revealed that SpaceShip Two fell far short of standards historically used for many spacecraft, according to a veteran former project engineer, with some critical systems potentially failing in thousands of flight hours, rather than hundreds of thousands of hours as typically tolerated.

"Time and money is needed to fix all that," the engineer added. "It becomes a much more expensive and much more exhaustive program than what [Virgin Galactic leadership] originally bought in to."

In its statement, Virgin said it is building a safety culture in which "risks are understood and their causes and controls [are] well evaluated."

The push to fly coupled with a lack of federally mandated safety standards hampered redesign of key systems, according to Frank Mayo, a veteran flight-controls engineer, who joined TSC in March 2013.

Mr. Mayo said he flagged his specific concerns to TSC leadership a year later. Testing showed that if the flight controls on either side of the vehicle jammed, both pilots pulling or pushing to free them would likely buckle the healthy side, potentially causing a loss of control, he wrote in an engineering report reviewed by the Journal. As a result, he said he urged the craft be grounded pending a redesign, though. His concerns apparently aren't connected to the events that investigators believe contributed to the crash.

In an interview, Mr. Mayo said soon after he raised his concerns his contract wasn't renewed and he left TSC in April 2014. In August, he sent an email to the FAA laying out his concerns and to the NTSB following the accident. The FAA had no immediate comment.

According to Virgin Galactic, "a small redesign" resolved a concern related to the one expressed by Mr. Mayo.

Mr. Mayo in an interview disputed Virgin's claim, and said the earlier small redesign of a broken bracket didn't address the concerns he brought to senior management.

Write to Andy Pasztor at andy.pasztor@wsj.com and Jon Ostrower at jon.ostrower@wsj.com

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