DHL Express’s contracted pilots in the U.S. authorized a strike, increasing labor problems for the shipping company ahead of the German parent’s annual shareholder meeting. About 2,000 employees flying for five DHL network cargo carriers approved the labor action, which still has to go through a formal regulatory process and may be delayed. About 99 percent of the votes at Atlas Air Inc., Polar Air Cargo Inc., Southern Air Holdings Inc., ABX Air and Kalitta Air were in favor. The five carriers are contracted by DHL to provide service in North America and account for 70 percent of DHL’s total flying worldwide, according to a statement from the pilots’ union. A labor walkout could affect online retail giant Amazon.com Inc., which has signed agreements for air cargo services recently with the parent companies of Atlas and ABX, according to a release from the International Brotherhood of Teamsters Local 1224, which represents the pilots. Air Worldwide Holdings controls Atlas, while ABX is an Air Transport Services Group unit. The pilots are upset at the disparity between their wages and the pay at bigger shippers United Parcel Service Inc. and FedEx Corp., a disagreement over work rules and a lack of job security, said Daniel Wells, the union president. DHL Express parent Deutsche Post DHL Group is holding its annual shareholders meeting Wednesday.