China Airlines began evaluating the repairs in 2001. The workers took photographs of 31 different doublers on different 747s, including the one on B-18255. Although there was a stain on the doubler, the workers chose to ignore it. The stain was actually caused by smoke as passengers were allowed to smoke until 1995. The smoke was forced out through the crack and nicotine stained the plane's skin. It was said in Mayday that if China Airlines went on to find out how the stain formed, they may find out the cracks and prevent the crash.