Sean O'Keefe said on Wednesday that NASA “got the point” of a report which said the space agency's culture contributed significantly to the Columbia shuttle disaster.
"This is a very seminal moment of this agency's history. Our strength and resolve will be tested," O'Keefe said.
He promised to read every word of the 250-page report and use it as "a roadmap to fix the problem" with an eye toward eventually resuming flights.
Appearing to tread cautiously, however, he has not yet set a date for the resumption of flights.
Earlier this month, NASA's associate administrator of space flight, Bill Readdy, called for flights to resume between 11 March and 6 April.
But according to O'Keefe, "it's gonna be a long road".
"Our challenge will be to choose wisely the options to fully comply with these (the report's) recommendations," he said.
Although criticised for not respecting security procedures, NASA's space shuttle programmme was described by the Columbia Accident Investigation Board as "not inherently unsafe".
The CAIB made a series of technical recommendations to Congress to avoid another disaster.
The crew of the Columbia were
killed shortly after takeoff
For example, NASA has to work to ensure shuttles do not shed potentially fatal foam shards on future launches.
The report also revealed a rescue bid could have been launched to save Columbia's astronauts if NASA had realized how critically the shuttle had been damaged during takeoff.
NASA is starting to implement changes recommended by the board, including the installation of new cameras to monitor launches.
The space agency is also working on reinforcing the carbon panels that protect the vulnerable leading edge of the shuttle's wing.
The board's report, released on Tuesday, also recommends establishing an independent technical authority to oversee safety for the shuttle programme.
Columbia, which exploded after takeoff in February killing all seven crew, was the second shuttle to be lost after the Challenger in 1986.
NASA currently has three surviving shuttles: Atlantis, Endeavour and Discovery.