The head of the U.S. space agency, NASA, told Congress Wednesday that there were no indications of trouble with the space shuttle fleet before the Columbia disaster. NASA administrator Sean O'Keefe appeared before a joint Senate-House of Representatives committee investigating the February 1 shuttle accident.

At the hearing, Arizona Senator John McCain read from two conflicting reports from NASA officials. One said that the shuttle fleet was safer than ever. But the author of the second reported stated, "in all my years of involvement, I've never been as concerned for space shuttle safety as I am right now." "How do we reconcile those two statements by two highly-regarded individuals who are within the bureaucracy of NASA?," said Senator McCain.

Mr. O'Keefe said the report's concerns were over future missions, not the safety of the shuttle fleet at the time. "There was no indication that I knew of that raised concerns along the way of current flight operations," he said. "If anything the diligence I see among the entire folk among the NASA community is that of a culture that's dedicated to ensuring safe flight operations."

Mr. O'Keefe said the agency calls off a mission if there's the slightest doubt about safety. For example, he said, when a tiny crack was found on one of the main engines on space shuttle Atlantis, the entire shuttle fleet was grounded for four months until the problem was fixed.

Some members of Congress asked whether NASA's shrinking shuttle budget had forced the agency to cut corners on safety. Mr. O'Keefe said private companies that run many shuttle operations are given incentives to reduce problems. As a result, he said, shuttle operations are running smoother and cheaper. "The reduction of in-flight anomalies, technical scrubs have dropped by a lot," he said. "What it appears to suggest here, is a case where efficiencies have been obtained and risk has been reduced."

Several members of Congress raised concerns that the independent board that took control of NASA's investigation last week would not be truly independent. Tennessee Representative Bart Gordon said the board appears biased in NASA's favor. "There seems to be a clear disconnect from your statements about the board's independence, and the rules you're laying down for the board. Let me quote just a few examples of your rules," said Mr. Gordon. "The current board not only includes NASA employees, but you also require it to be staffed by NASA employees, who will help write the board's final report, which will go to you."

Mr. O'Keefe said he and investigation board chairman, Admiral Harold Gehman, would work out Congress's concerns immediately. Mr. O'Keefe said he shared the same goal as Congress -- to find out what went wrong, and to fix it.