AIRLINES

United, Lufthansa to Form Alliance: United Airlines Inc. and Lufthansa Airlines will announce Monday that they are joining forces for travel between the United States and Germany, a move that could boost the role of Washington’s Dulles International Airport as a European gateway, industry sources said. The accord was made possible by the recent U.S.-German bilateral aviation agreement. The agreement, to be signed Monday, would designate Washington, Chicago and San Francisco as “gateway cities,” the sources said.