But because of the Columbia accident, critics are wondering if the plan is still valid.

He also was a key player on several "tiger teams" during the investigation into the cause of the Columbia accident in 2003.

The inspection has been standard procedure ever since the 2003 Columbia accident.

Moreover, after the Columbia accident, the manned space program seems to lack focus and a sense of mission.

The center manages the external tank that has been implicated in the Columbia accident.

Discovery is completing only the second shuttle flight since the Columbia accident three years ago.

The 106-page report covers the year immediately preceding the Columbia accident and did not comment on it directly or the investigation into its cause.

Because of the Columbia accident, he said, he decided to defer his plans and help with the investigation.

Still, the board faces unique problems in investigating the Columbia accident.

Since the Columbia accident, the space station has had crews of two rather than three to conserve resources.