Crash Course in Density As flight 143, a twin engine 767, was passing over Red Lake on its was to Edmonton, Canada, the left front fuel pump warning light went on. There were a few possibilities for this to happen, such as the fuel pump failing, a fuel line clogging, or a empty fuel tank. The former two were easily dealt with, since the plane could fly without one fuel pump. However, the last possibility was horrifying. After a few minutes, the second fuel pump in the left wing began to blare. It would be too much of a coincidence for two fuel pumps to independently fail, or two fuel lines to independently