Over the past four and a half decades, the so-called D.B. Cooper skyjacking case has captivated countless armchair detectives - not to mention teams of FBI investigators - hoping to finally crack the nation's only unsolved act of air piracy. Now a California man, who has assembled a team of investigators, thinks he may have finally solved case, which will be detailed in the two-part History Channel special D.B. Cooper: Case Closed? that airs on Sunday and Monday..