United Airlines CEO Scott Kirby celebrates the opening of a new addition to its Flight Training Center in Denver, Colorado, on Feb. 22, 2024.United Airlines CEO Scott Kirby says he is optimistic about Boeing's recovery after meeting with the manufacturer's new chief executive. It's an upbeat change of tune from the head of United, a top Boeing customer that has been among the most publicly frustrated about the planemaker's problems, which have led to delayed deliveries of dozens of aircraft.Kirby and Boeing ...