The labor union of Hyundai Motor Co. launched a full-day strike Friday after failing to reach an agreement with management over wages, raising concerns about further production disruptions amid sluggish vehicle sales. It marks the first time in 10 years that the automaker's union has staged an eight-hour strike. Production lines at Hyundai Motor's plants in Ulsan, Jeonju and Asan are set to be halted for a combined 16 hours across two work shifts, with about 39,000 union members participating in the walkout. Including Friday's walkout, the union has staged a combined 60 hours of strikes since wage talks with management began in May. The continued strikes are estimated to result in cumulative production losses of around 55,200 vehicles, with lost sales exceeding 2.3 trillion won ($1.64 billion), according to industry sources. Production disruptions are expected to worsen as the union plans additional four-hour walkouts Monday and Tuesday. The latest labor action comes after management and the union failed to narrow their differences over wages, a proposed 50 percent increase in performance-