An independent report into the fatal break up of the Columbia space shuttle has concluded that flawed practices at the US space agency (Nasa) were "as much a cause" of the tragedy as technical faults.
Columbia's left wing was fatally damaged during lift-off
Following are extracts of the report by the Columbia Accident Investigation Board (CAIB).
"From the beginning, the board witnessed a consistent lack of concern about the debris strike on Columbia.
"Nasa managers told the board 'there was no safety-of-flight issue' and 'we couldn't have done anything about it anyway.'
"The investigation uncovered a troubling pattern in which shuttle programme management made erroneous assumptions about the robustness of a system based on prior success rather than on dependable engineering data and rigorous testing.
"The physical cause of the loss of Columbia and its crew was a breach in the thermal protection system on the leading edge of the left wing.
"The breach was initiated by a piece of insulating foam that separated from the left bipod ramp of the external tank and struck the wing in the vicinity of the lower half of reinforced carbon-carbon panel 8 at 81.9 seconds after launch.
"During the re-entry, this breach... allowed superheated air to penetrate the leading edge-insulation and progressively melt the aluminium structure of the left wing, resulting in the weakening of the structure until increasing aerodynamic forces caused loss of control, failure of the wing, and break up of the orbiter.
"The destruction of the crew module took place over a period of 24 seconds beginning at an altitude of approximately 140,000 feet.
"The rescue was considered challenging but feasible.
"If programme managers were able to unequivocally determine before Flight Day Seven that there was potentially catastrophic damage to the left wing, these repair and rescue plans would most likely have been developed, and a rescue would have been conceivable.
"To succeed, it required problem-free processing of Atlantis (Nasa's space shuttle) and a flawless launch countdown.
"...accelerating processing of Atlantis might have provided a window in which Atlantis could rendezvous with Columbia before Columbia's limited consumables ran out.
"The shuttle programme's complex structure erected barriers to effective communication and its safety culture no longer asks enough hard questions about risk.
"By the eve of the Columbia accident, institutional practices that were in effect at the time of the Challenger
accident (1986) - such as inadequate concern over deviations from expected performance, a silent safety programme, and schedule pressure - had returned to Nasa.
In this context, the board believes the mistakes that were made on STS-107 (Columbia) are not isolated failures, but are indicative of systemic flaws that existed prior to the accident.
"...ineffective leadership... failed to fulfil the implicit contract to do whatever is possible to ensure the safety of the
"Nasa's organisational culture and structure had as much to do with this accident as the external tank foam.
"The board strongly believes that if these persistent, systemic flaws are not resolved, the scene is set for
"The White House, Congress and Nasa leadership exerted constant pressure to reduce or at least freeze operating costs (for the space shuttle).
"Over the past decade, there has been a reduction of approximately 40% in the purchasing power of the (Shuttle) programme's budget, compared to a reduction of 13% in the Nasa budget overall.
"...safety and support upgrades were delayed or deferred, and shuttle infrastructure was allowed to