SEWARD, Neb. (AP) – A federal investigator doesn’t expect a quick answer to the question facing him: What caused the fatal plane crash near Seward airport in southeastern Nebraska? The crash of the Christen Eagle II biplane into a cornfield Sunday morning killed 58-year-old Jeff Clausen, of Lincoln, and 56-year-old Mark Pearson, of Plymouth. At a news conference Monday, National Transportation Safety Board investigator Tim LeBaron said he’d spent much of Labor Day the crash site near Seward Municipal Airport. LeBaron says he expects to have some information available in about a week, but his full investigation could take six months. The Lincoln Journal Star reports that Pearson had just bought the plane and was flying it under the instruction of Clausen, who was director of operations for Lincoln’s Silverhawk Aviation.