Washington ? Vowing not to “sit here on our hands” while awaiting a report from Columbia investigators, NASA Administrator Sean O’Keefe said Friday that his agency had begun planning to return to space, perhaps as soon as this fall.

O’Keefe and William Readdy, NASA’s associate administrator for space flight, said that fulfilled a promise they made to families of the seven astronauts killed when the space shuttle broke up Feb. 1 over Texas.

They emphasized that NASA would wait until the Columbia Accident Investigation Board issued its findings and recommendations before committing to a launch date. However, O’Keefe said there was no reason to suspend all planning in the interim.

Readdy this week ordered the formation of a “Return to Flight” team and the drafting of a preliminary plan by April 1. Among other things, the team will conduct a “thorough review of the adequacy and robustness of key space shuttle systems, such as the insulation approach currently in use on the External Tank,” his memo states.

Investigators are trying to determine whether a chunk of insulating foam from the tank that struck Columbia’s wing during launch damaged it enough to lead to the disaster.

“Much needs to be done as we move forward to fly again,” Readdy concluded in his memo. “I anticipate that our processes will be strengthened and that the safety of flight will be enhanced as we return to flight.”

The return to flight team also will review ways to inspect and repair damaged tiles while the shuttle is in orbit and examine methods to identify in-flight safety problems and how those issues are relayed to top NASA management.

The orbiter Atlantis is towed out of the vehicle assembly building Friday at the Kennedy Space Center in Cape Canaveral, Fla. Atlantis was to be the launch after Columbia, taking a replacement crew to the international space station. The mission is on hold, although NASA officials said Friday they hoped to resume shuttle flights this fall.

Plans call for the next shuttle mission to be directed toward continuing the construction of the International Space Station.

Three crew members now on the station, Expedition 6, will be replaced by next month by two crew members who will get there aboard a Russian Soyuz craft. The Expedition 6 crew will return to Earth on a Soyuz now docked at the station.

Barring an unexpected finding by the investigation board, NASA will continue to assume that the remaining three shuttles can be flown safely for at least another decade and possibly until 2020, O’Keefe said. He and other NASA managers meet next week with officials at the agency’s Michoud Assembly Facility in New Orleans to discuss what efforts might be required to keep the fleet flying.