Jet accident probe expands to include Boeing supplier

As authorities probe Boeing’s safety protocols as part of their investigation into what went wrong with a flight that blew a hole midair last week, the role of a major supplier is also coming into focus: Spirit AeroSystems. The Kansas-based company, which is far less prominent than Boeing, built most of the jet before handing it off to the aviation giant. On Wednesday, Spirit said it had started working directly with the National Transportation Safety Board on its investigation — a sign that investigators believe Spirit may have critical information relevant to the probe.