The independent group overseeing NASA's effort to resume shuttle flights said Friday the agency has completed the first steps toward returning to space.

After the Feb. 1, 2003, accident that destroyed the space shuttle Columbia (search) and killed all seven astronauts aboard, investigators recommended 15 changes.

NASA has completed three changes and is putting into place most of the other recommendations, said Joseph Cuzzupoli, who oversees the technical panel of the Return to Flight Task Group (search).

"The progress that has been made by NASA in implementing the recommendations of the Columbia Accident Investigation Board are substantial," said former shuttle commander Richard Covey, who is leading the task group.

The investigation concluded that NASA's overconfident management and inattention to safety doomed Columbia just as much as the chunk of foam that struck the shuttle with deadly force. Without drastic changes, the report said, another disaster is likely.

Covey said there is still much work to be done before NASA is "truly ready to return to flight."

One of the main obstacles may be finding enough personnel with the expertise to achieve the goals, said Dan Crippen, chairman of the group's management panel.

"It is no surprise to anybody that every independent group that comes by drops another requirement on NASA and NASA has been the beneficiary of many suggestions about its organization, culture and things to do before it gets to go fly again," said former astronaut James Adamson, who leads the return-to-flight operations panel.

"With a limited pool of talent, depending on how you manage it, it could become a resource constraint or it could become a risk or it may be none of these."

Adamson said the group and NASA are aware of potential problems that could arise due to mismanagement of cost, schedule and the volume of work that needs to be done by next spring, when the next shuttle launch is expected.

The task force is watching closely to make sure NASA "doesn't elevate the risk," Adamson said.

The group say NASA has met recommendations to:

— Revisit its agreements with the National Geospatial-Intelligence Agency.

— Audit all major shuttle projects and elements, and implement a new policy that two NASA employees must attend all foam hand-spraying procedures and final reviews of all flight hardware.

— Implement a comprehensive inspection plan for the shuttle's thermal protection system.

"There is no doubt that this vehicle will be the most safe vehicle that has ever flown," Cuzzupoli said.