Delta Air Lines is eyeing New York and Los Angeles as the main bases for Bombardier’s new jetliner next year, offering a glimpse of how carriers can add service economically with the midsize plane. Dallas is also likely to get a lot of C Series flights, Delta said in an internal memo to pilots. That sets up a test of the carrier’s ability to use the single-aisle aircraft to attract customers in the backyard of American Airlines and Southwest Airlines. Delta is the first major US carrier to buy the C Series, a midrange aircraft that offers roomier interiors than regional jets while typically carrying fewer passengers than a plane from the Boeing 737 or Airbus A320 families. The Bombardier aircraft should enable airlines to offer comfy rides to midsize cities without flooding the market with too many seats. <br/>