United Airlines flight attendants have approved a new labor contract that will bring their first pay increases in six years — along with boarding pay, a long-sought change that compensates crew members for the work they do before the plane leaves the gate. The five-year agreement, ratified on Tuesday, covers nearly 30,000 flight attendants at United. It includes an average 31% pay increase this summer, boarding pay worth an additional 7% to 8% in compensation on average and $741 million in retroactive pay, according to the Association of Flight Attendants. “The contract will immediately change the lives of United Flight Attendants, especially our thousands of new hires who have been hired since the pandemic,” said Ken Diaz, president of the union’s United chapter.…