New and troubling questions are emerging about what caused the Air India crash that killed 260 people. A preliminary investigation ruled out mechanical issues and found that the plane's fuel cutoff switches had been flipped seconds after takeoff. Experts believe it’s most likely that one of the pilots was responsible. William Brangham discussed more with aviation correspondent Miles O’Brien. PBS News is supported by - https://www.pbs.org/newshour/about/funders