On 9 October 2007, NASA's Engineering and Safety Center, an independent review group set up after the 2003 "Columbia" disaster, advised replacement of three of "Discovery's" reinforced carbon-carbon (RCC) panels on the leading wing edge, due to a loss of small amounts of the protective silicon-carbide coating. NASA reviewed the issue of oxidation of the panels for several months, using a variety of specialized testing methods, including thermography. These tests showed that the panels had not worsened over the course of the past two flights of "Discovery", and the orbiter project engineers concluded in August that "Discovery" was safe to launch as is. Had a decision been made to repair the panels, the orbiter would have been rolled back to the VAB, delaying the launch.