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, a copy of which was reviewed by Bloomberg News. That sets up a test of the airline's ability to use the single-aisle aircraft to attract customers in the backyard of American Airlines Group and Southwest Airlines.

Delta is the first major U.S. 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 Co. 737 or Airbus SE A320 families. The Bombardier aircraft, which the Montreal-based company has spent at least $6 billion to develop, should enable airlines to offer comfy rides to midsize cities without flooding the market with too many seats.

"From the standpoint of operating costs, from the standpoint of ownership costs, it's an ideal aircraft for these not-quite-mainline markets," said Robert Mann, an aviation consultant and former airline executive. "If it performs as advertised, reliably, it's going to be a real game-changer."

Morgan Durrant, a spokesman for Delta, declined to comment on the memo. The aircraft is scheduled to enter service for the Atlanta-based airline in the second quarter of 2018, according to the Aug. 7 notice to pilots, which described preliminary plans for the planes.

The U.S. airline ordered at least 75 of the CS100 models last year in a deal valued at $5.6 billion. The purchase threw a lifeline to Bombardier after the C Series program came in two and a half years late and more than $2 billion over budget.